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The  Trial   Case 
and  How  to   Use  It 


A  Practical  Treatise   For 
Optometrists 


Illustrated 
Second  Edition 


By 
R.   M.    LOCKWOOD 

Author  of  Principles  of  Optometry,   Some   Experiments  in  Optics, 
Subjective  Tests  for  Difficult  Cases,  Etc. 


NEW    YORK 

FREDERICK   BOGER   PUB.   CO. 
I    Maiden   Lane 


X 


OPTOMFTRY 


Copyright    i  904 

by 

Frederick   Boger    Pub.    Co. 

I    Maiden  Lane 

New  York 


V 


PRESS    OF 

(^t)C  <©ptical  Journai 


OPTOMETRY 
LIBRARY 


LIST  OF  ILLUSTRATIONS. 


PAGE 

The   Eye    8 

A  Normal  Eye lo 

Emmetropic   Eye    14 

Myopic   Eye    14 

Hypermetropic  Eye   14 

Test  Types    20 

Clock  Dial  Chart 21 

Types   of   Lenses 21 

Cylinders    22 

Prisms    23 

Pin-hole  Disc    25 

Stenopeic  Slit   25 

Maddox   Rod    26 

Double  Prisms    2y 

Cobalt  Blue  Disc 28 

Trial  Frame    30 

^Measuring  Card   3^ 

Trial  Case   33 

Test  Types    34 

Children's  Test  Types 35 

Prav's   Letter   Chart 36 

Fan  Chart  37 

A  Landscape  Out  of  Focus 44 

A  Landscape  in  Focus 45 

An  Adjustable  Outfit 53 

Lenticular    Lenses    67 

Toric    Curves    69 

Removing  the  Cinder 7^ 

Tool  for"  Removing  Cinders 77 


V 


PREFACE   TO   THE    SECOND   EDITION. 

The  very  cordial  reception  which  has  been  accorded  to  this 
work  whereby  the  first  edition  becomes  exhausted  in  six  months, 
is  extremely  gratifying  to  the  author,  who  feels  that  the  series  of 
practical  works  of  which  the  present  volume  is  the  second  really 
fills  a  want  among  those  who  make  eye  testing  a  profession.  He 
feared  that  optometrists  might  not  care  to  freshen  up  on  the 
details  of  their  work,  but  the  result  has  proved  this  not  to  be 
true.  In  the  first  volume  of  the  series,  "Principles  of  Optome- 
try," he  presented  the  principles  as  against  the  science  of  optom- 
etry ;  in  the  present  volume  he  gives  the  routine  practice  for 
ordinary  cases  as  he  follows  it,  while  in  "Subjective  Tests  for 
Difficult  Cases"  he  presents  a  great  many  practical  methods  for 
those  cases  where  the  routine  method  is  undesirable  or  where  a 
re-examination  is  necessary. 

The  author  has  carefully  prepared  the  text  of  this  second 
edition.  He  has  made  a  few  corrections  and  slight  additions  to 
give  greater  clearness,  but  otherwise  the  work  remains  the  same 
as  in  the  first  edition. 


CHAPTER  I. 

THE  EYE  AND  SOME  OF  ITS  FUNCTIONS. 

THE  EYE. — The  eye  is  the  same  as  a  photographic  camera 
so  far  as  its  image-producing  power  is  concerned,  and  corresponds 
to  a  lens  of  something  less  than  an  inch  focus.  It  differs  from  a 
camera  in  the  fact  that  it  is  not  a  simple  lens  or  a  combination  of 
simple  lenses  forming  an  image  in  the  air  at  a  certain  dis- 
tance to  the  rear,  but  rather  a  succession  of  transparent  refracting 
living  substances  forming  altogether  one  solid  whole.  Com- 
mencing at  the  front  is  the  cornea,  the  transparent  portion  of  the 
eye  which  is  exposed  to  the  outside  world.  Behind  this  comes 
the  aqueous  chamber,  so  called  because  of  the  watery-like  fluid 
which  it  contains;  next  the  crystalline  lens,  which  is  bi-convex 
in  form,  then  the  vitreous,  a  jelly-like,  transparent  medium,  and 
finally  the  retina,  or  the  screen  of  the  eye,  on  which  the  image 
made  by  the  succession  of  transparent  bodies  just  specified  forms 
a  copy  of  external  objects.  The  retina  is  really  an  expansion 
of  the  optic  nerve  which  consists  of  hundreds  of  thousands  of 
individual  fibres,  entering  the  ball  of  the  eye  from  the  rear  and 
then  spreading  out  on  the  inner  surface  of  its  hindermost  por- 
tion to  form  the  retinal  screen.  This  retinal  screen  is  very  com- 
plex ;  is  made  up  of  nine  distinct  layers,  all  transparent,  but  the 
deepest  one  of  all  considered  to  contain  those  peculiar  organs,  the 
rods  and  cones,  which  are  now  supposed  to  fulfill  the  function  of 
responding  to  the  waves  of  light  in  such  a  way  that  the  vibrations 
which  they  transmit  to  the  fibers  of  the  optic  nerve  are  carried  by 


8  THE    TRIAL    CASE    AND    HOW    TO    USE   IT. 

the  latter  to  tlie  visual  centers  uf  the  brain,  there  to  be  interpreted 
in  that  mysterious  way  which  we  call  vision. 

The  eye  is  a  globe,  or  almost  one,  of  a  diameter  of  about  one 


S. — The  sclerotic. 

V. — The   viti'eous  humor. 

Oh. — The  choroid. 

Y. — The  macula  lutea. 


Figure  1.— THE  EYE. 
A. — The  aqueous  humor. 


R. — The  retina. 
I. — Iris.  O. — Optic  nerve. 

T.. — The  crystalline  lens.  C. — The  cornea. 

M. — The  ciliary  muscle.  P. — The  pupil. 

X. — The  centre  of  rotation  of  the  eye. 
J  he  dotted  circle  shows  the  departure  of  the  normal  eye  from  a  spherical  form 


THE    EYE    AND    SOME    OF    ITS    FUNCTIONS.  0 

inch.  Its  outer  coat  is  very  tougli,  far  more  so  than  it  looks,  and 
this  outer  coat  consists  of  three  distinct  layers.  The  inner  one, 
the  retina,  has  already  been  referred  to.  Next  to  and  outside  of  it 
is  the  choroid,  which  is  thin  and  dark  purple,  and  contains  most 
of  the  blood  vessels  which  feed  the  eye  and  carry  off  the  products 
of  decay,  for  the  eye  is  a  physiological  instrument  and  like  all  the 
other  organs  of  the  body  it  is  continually  wearing  out  and  being 
renewed,  or  in  other  words  there  is  a  continual  circulatory  current 
in  the  eye,  and  in  all  parts  of  the  eye,  which  constantly  brings 
in  new  food  and  carries  away  waste  products.  It  is  true  that  it  is  all 
transparent,  or  rather  so  in  health,  but  at  the  same  time  this  circu- 
lation is  absolutely  necessary,  and  its  cessation  for  any  reason 
means  blindness  in  a  few  hours,  while  a  partial  choking  up  of 
the  ducts  is  very  apt  to  seriously  interfere  with  vision  and  ulti- 
mately destroy  it.  Immediately  outside  of  the  choroid  is  the 
sclerotic  coat,  which  is  white  and  very  tough.  At  the  front  of  the 
eye  this  coating  becomes  transparent  and  then  is  known  as  the 
cornea. 

In  the  center  of  the  cornea  is  the  pupil,  which  is  merely  the 
central  portion  not  covered  by  the  iris.  It  looks  black,  but  is 
really  transparent.  The  reason  we  cannot  see  through  it  ordina- 
rily is  that  to  see  anything  through  a  transparent  substance  there 
must  be  something  more  or  less  lighted  up  behind  it,  but  in  the 
case  of  the  eye  the  only  way  for  the  retina  to  be  lighted  up  is 
through  the  pupil,  and  this  will  never  occur  so  long  as  our  head  is 
in  the  way  of  the  light,  which  it  will  always  be  when  we  attempt  to 
look  inside.  By  reflecting  light  into  the  eye  from  a  mirror,  in 
the  center  of  which  there  is  a  tiny  hole,  through  which  we  look, 
we  will  then  see  the  back  of  the  eye,  and  the  pupil  will  appear 
bright  red,  or  orange,  instead  of  black,  this  due  to  the  capillary 


10  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

network  of  blood   vessels  of  the  choroid   showing  through   the 
transparent  retina. 

The  eye  is  subject  to  many  diseases,  with  very  few  of  which 
the  optometrist  can  have  any  concern.  The  main  thing  that  he 
should  know  in  this  connection  is  to  detect  opacities,  whether  due 
to  cataract  or  to  some  other  cause ;  and  to  be  able  to  tell  by 
simple  inspection  whether  there  is  anything  abnormal  in  the  visible 
portions  of  the  eye.  For  this  purpose  a  condensing  lens,  the 
concave  mirror  and  the  ophthalmoscope  are  used. 


Fig.  2.— a  normal  EYE. 

One  in  which  parallel   rays  of  light  focus  on  the  retina  when   the  eye  is  in   a 

state  of  physiological  rest. 

A  NORMAL  EYE. — From  the  point  of  view  of  the  optome- 
trist a  normal  eye  is  one  which  when  it  is  in  a  state  of  physio- 
logic rest  it  can  look  upon  far  distant  objects  and  see  them  dis- 
tinctly;  that  is,  the  image  of  the  distant  object  formed  on  the  retina 
will  be  without  the  slightest  diffuseness  of  image.  Such  an  eve  is 
extremely  rare,  but  it  serves  as  a  standard  of  comparison  by 
which  we  may  express  the  dioptric  condition  of  any  eye  wdiich  is 
under  test.  Such  an  eye  is  said  to  be  emmetropic.  When  the  eye 
is  abnormal  from  an  optical  point  of  vicw^  we  call  it  ametropic. 


THE    EYE    AND    SOME    OF    ITS    FUNCTIONS.  11 

It  is  the  sphere  of  optometry  to  supply  f;lasses  to  anietropic  eyes 
to  bring-  them  as  near  to  emmctropia  as  the  physiological  and 
optical  conditions  will  permit. 

ACCOMMODATION.— Just  back  of  the  iris  where  it  meets 
the  sclerotic  is  a  small  circular  muscle  attached  to  a  membrane, 
to  the  center  of  which  is  fastened  the  crystalline  lens.  Although 
the  eye  is  a  camera,  there  is  one  important  point  in  which  it 
differs  from  all  others  cameras.  Its  screen  is  fixed,  and  in  order 
to  see  distinctly  for  all  distances  it  must  change  its  magnifying 
power.  With  an  ordinary  lens,  the  nearer  the  bright  object  on  one 
side  of  the  lens,  the  farther  away  must  be  the  image  on  the  other 
side  of  the  lens,  but  with  the  eye  there  can  be  no  movement  of  the 
screen  which  receives  the  image,  hence  the  power  of  the  lens 
itself  is  altered.  The  more  the  crystalline  lens  swells  in  the  center 
the  greater  its  strength,  and  the  greater  its  strength  the  nearer  the 
object  must  be  to  be  seen  distinctly.  It  is  the  function  of  the  small 
circular  muscle  to  produce  these  changes  in  convexity  by  loosen- 
ing up  the  membrane,  so  that  as  this  loosening  occurs  the  crystal- 
line lens  swells.  This  property  of  the  eye  is  called  its  accommo- 
dation. It  is  strongest  in  childhood,  but  steadily  diminishes  in 
power  as  we  grow  older  until  at  about  65  years  of  age  there  is 
no  more  accommodation,  and  the  eye  is  only  in  focus  for  just 
one  point.  This  ocular  process  is  called  presbyopia  and  all  hu- 
man beings  without  exception,  are  subject  to  it.  As  a  result  of 
it  all  persons,  except  a  few  very  near-sighted  ones,  must  wear 
glasses  eventually  to  read,  while  others  must  also  wear  glasses  to 
see  well  at  a  distance. 

FAR  AND  NEAR  POINTS.— These  are  the  two  points 
which   express  the  limits  of  the   accommodative   power   of   the 


13  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

individual.  In  the  case  of  a  myope  they  have  an  actual  existence, 
and  the  same  is  the  case  with  an  emmetrope.  In  the  former  case 
the  two  points  will  be  within  infinity,  one  being  the  greatest  dis- 
tance at  which  the  eye  can  see  clearly  and  the  other  the  nearest 
point  at  which  it  can  see  clearly.  In  the  case  of  the  emmetrope  one 
will  be  at  infinity,  but  with  a  hypermetrope  only  one  of  the 
points,  the  near  point,  can  have  an  actual  existence,  and  where 
the  hypermetropia  is  high  both  points  may  be  beyond  infinity; 
that  is  to  say,  they  will  have  no  actual  existence,  the  eye  not 
being  able  to  focus  any  rays  on  the  retina  whether  near  or  far.  In 
this  case  they  may  be  said  optically  to  be  behind  the  patient's  back. 

HYPERMETROPIA.— When  the  eyeball  is  deficient  in 
depth,  or  the  dioptric  power  of  the  crystalline  lens  of  the  eye  is 
too  low,  then  we  have  a  condition  called  hypermetropia  or  hyper- 
opia. In  this  ocular  condition  the  ciliary  muscle  must  act  to 
increase  the  powder  of  the  crystalline  lens  so  that  the  image  of  the 
distant  object  instead  of  blurring  on  the  retina  may  form  there 
a  clear  and  distinct  image.  This  puts  a  great  deal  of  work  on  the 
delicate  ciliary  muscle  as  compared  wath  that  of  the  emmetropic 
eye,  in  which  there  is  no  strain  at  all  on  this  muscle.  The  pos- 
sible results  of  this  condition  are  several.  First  the  eye  will 
show  presbyopia  before  it  would  were  the  eye  strictly  normal. 
Usually  with  the  normal  eye,  glasses  are  needed  for  reading  about 
42  years  of  age,  but  with  an  eye  which  is  hypermetropic  to  a  high 
degree  this  necessity  may  arise  many  years  sooner,  while  in  some 
extra  high  cases  the  glasses  are  needed  in  childhood.  The  aver- 
age eye  has  just  about  so  much  ciliary  power,  and  if,  as  is  the  case 
with  a  hypermetropic  eye,  half  of  this  is  used  to  overcome  the 
optical  abnormality  of  the  eye,  then  only  half  of  it  is  left  for  a 


THE    EYE    AND    SOME    OF    ITS    FUNCTIONS.  13 

reserve,  which  will  of  course  be  used  up  long  before  the  tra- 
ditional age  of  42.  The  second  difficulty  which  arises  with 
hypermetropic  eyes  is  headache  and  eyestrain.  Each  individual 
has  a  certain  amount  of  nervous  force,  and  while  there  are  some 
who  can  give  up  the  amount  demanded  by  the  ciliary  muscle  in 
hypermetropia,  there  are  others  which  even  with  a  very  small 
amount  of  it  will  suffer  from  headache,  especially  after  sight- 
seeing, as  well  as  from  eyestrain,  and  in  some  extraordinary 
cases  from  several  remote  nervous  reflexes.  Finally  the  ciliary 
muscle  may  take  on  a  condition  of  "spasm"  or  "cramp,"  in  which 
as  the  result  of  overwork  the  muscle  may  suddenly  contract  into 
a  fixed  position  and  simulate  myopia.  There  is  considerable 
difference  of  opinion  as  to  the  nature  of  this  spasmodic  condition, 
some  claiming  that  it  a  persistent  spasm  hard  to  break  up,  others 
that  it  is  only  effective  when  the  eye  is  in  use,  and  that  by  "fog- 
ging" the  spasm  will  relax.  Tscherning  dismisses  the  whole 
subject  with  the  statement  that  "all  spasm  of  the  accommodation 
will  relax  promptly  in  the  dark  room."  If  this  is  true  then  cer- 
tainly "fogging"  is  all  that  is  necessary.  In  any  event  the  op- 
tometrist must  be  constantly  on  his  guard  not  to  be  deceived  and 
prescribe  the  wrong  lenses. 

MYOPIA. — When  the  eyeball  is  too  long,  or  the  dioptric 
power  of  the  crystalline  lens  of  the  eye  is  too  strong,  then  we 
have  a  condition  of  myopia.  In  order  that  the  image  of  a  given 
object  shall  come  clear  on  the  retina,  the  power  of  the  crystalline 
lens  must  weaken,  but  there  is  a  limit  to  this,  which  is  reached 
when  the  ciliary  nuiscle  is  entirely  relaxed.  Myopes  cannot  see 
at  a  distance,  but  do  not  have  to  wear  reading  glasses  so  soon  as 
emmetropes  and  hypermctropes ;  in  fact,  some  of  them  never  have 


14  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

to  wear  them.  For  a  normal  eye  in  a  young  person  the  range  of 
vision  may  be  from  6  inches  to  infinity,  while  in  a  myope  it  may 
only  be  from  4  to  13  inches.  In  both  case  the  eyes  have  about 
equal  accommodative  powers.  It  was  laid  down  by  Bonders,  and 
many  others  hold  the  same  opinion,  that  a  myopic  eye  is  always  a 
diseased  eye,  and  that  the  myopia  is  usually  progressive  and  is 
due  to  civilization ;  that  eves  were  not  meant  for  such  close  work 


Fig.   3. 
(a)    Emmetropic  eye.  {b)   Myopic  eye.  (e)    Hypermetropic  eye. 

as  is  common  in  schools,  though  of  late  years  this  opinion  given  out 
by  Bonders  has  been  somewhat  modified.  It  is  now  held  that 
there  are  two  sorts  of  myopia;  one,  non-malignant,  which  is  the 
result  of  school  life,  and  which  runs  to  a  certain  point  and  there 
stops,  and  the  other  the  true  malignant  variety,  which  has  noth- 
ing to  do  with  school.  Germany  is  the  home  of  the  myope  and  the 
condition  arouses  much  concern  there. 

ASTIGMATISM. — The  eye  is  far  from  being  optically  per- 
fect and  one  of  its  most  common  defects,  found  alike  in  emme- 
tropia  and  ametropia,  is  astigmatism.  This  means  that  ocidar 
condition  in  which  the  different  meridians  of  the  eye  have  not  the 
same  power.  If  we  put  before  such  an  eye  a  narrow  slit,  first 
vertical,  then  horizontal,  and  then  in  several  other  different  direc- 
tions, we  will  find  one  direction  in  which  it  shows  a  greater  power 
than  the  others,  and  we  will  find  another  in  which  the  power  is 


THE   EYE   AND    SOME    OF    ITS    FUNCTIONS.  15 

less  than  all  the  others.  The  two  directions,  one  having  the 
strongest  power  and  the  other  having  the  least,  are  the  two  prin- 
cipal meridians  of  the  eye.  Before  w-e  can  get  the  clearest  image 
possible  on  the  retina  we  must  make  all  the  meridians  of  equal 
power.  Astigmatism  is  extremely  common,  but  in  most  cases  of 
so  little  amount  that  the  owner  has  become  used  to  it,  and  in  fact 
is  better  satisfied  with  it  uncorrected  than  the  contrary,  but  where 
the  condition  is  at  all  marked  it  often  gives  rise  to  the  same  symp- 
toms as  hypermetropia  and  is  accompanied  with  poor  vision. 

USE  OF  CORRECTING  LENSES.— The  lenses  used  for 
the  correction  of  hypermetropia  are  those  which,  by  adding  diop- 
tric power  to  the  eye,  force  the  ciliary  muscle  to  give  up  an  equal 
amount,  and  thus  bring  about  a  normal  state  of  rest.  These  are 
plus  lenses,  those  which  have  a  magnifying  power.  For  myopia 
minus  lenses  are  given,  those  which  have  a  minifying  power. 
Their  effect  is  to  so  decrease  the  total  dioptric  power  of  the  eye  and 
lens  together  that  the  images  of  distant  objects  will  come  clear 
upon  the  retina.  For  astigmatism  we  must  use  cylinders,  either 
plus  or  minus,  as  the  case  may  require.  These  are  lenses  having 
their  curvatures  all  in  one  direction.  If  a  plus  cylinder  is  used  its 
greatest  power  is  so  placed  that  it  corresponds  with  the  weakest 
meridian  of  the  eye  and  thereby  makes  the  two  meridians  equal, 
or  else  if  a  minus  lens,  its  greatest  power  is  placed  at  right  angles 
to  the  highest  meridian  of  the  eye,  or  what  is  the  same  thing,  paral- 
lel and  coincident  with  the  meridian  of  lowest  power.  The  result 
in  either  case  is  the  same ;  all  the  meridians  are  made  alike  and  the 
combination  acts  as  a  sphere.  For  compound  troubles,  such  as 
hypermetropia  combined  with  astigmatism,  we  must  give  a  cylin- 
der combined  with  a  sphere.  These  form  wdiat  are  called  sphero- 
cylinders. 


16  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

The  retinal  image  of  an  astigmatic  eye  is  not  correct  but  for 
one  meridian  at  a  time,  and  advantage  is  taken  of  this  in  testing  for 
astigmatism.  The  eye  under  test  is  fogged,  that  is,  a  plus  lens  is 
placed  in  front  of  it  which  blurs  distant  object.  Then  the  patient 
is  directed  to  look  at  a  set  of  black  radiating  lines,  of  which  he 
will  see  those  in  one  direction  the  best.  This  direction  is  one 
of  the  principal  meridians  of  his  astigmatism.  The  other  is  at 
right  angles  to  it.  The  direction  of  a  cylinder  in  which  there  is 
no  power  is  called  its  axis. 

PRISMS. — Prisms,  though  having  no  magnifying  power,  are 
usually  included  under  the  general  name  "lenses"  when  all  the 
transparent  media  employed  in  the  correction  of  refraction  are  con- 
sidered together.  They  are  used  in  some  cases  of  heterophoria, 
where  this  cannot  be  dissipated  by  the  correction  of  the  ametropia, 
or  where  the  case  is  not  severe  enough  to  demand  an  ocular  opera- 
tion. 

DIOPTRIC  SYSTEM.— Lenses  are  now  numbered  as  fol- 
lows: A  lens  forming  on  a  screen  an  image  of  the  sun  at  a  dis- 
tance of  40  inches  is  of  i  diopter ;  a  lens  twice  as  strong,  or  one 
forming  an  image  of  the  sun  at  20  inches  is  a  2  diopter  lens  ;  a 
lens  which  is  three  times  as  strong,  forming  an  image  of  the  sun 
at  13  inches,  is  a  3  diopter  lens,  etc.  The  lenses  in  the  trial  case 
are  numbered  in  this  way.  To  find  the  value  of  two  or  more  of 
them  together  combine  the  values  as  shown  on  their  handles. 
The  old  system  was  based  on  French  inches,  which  are  not  ex- 
actly the  same  as  English  inches,  but  one  system  may  be  turned 
into  the  other,  accurately  enough  for  all  practical  purposes,  by  the 
following  rule :     To  change  from  diopters  to  inch  system  divide 


THE    EYE    AND    SOME    OF   ITS    FUNCTIONS.  17 

40  by  the  value  in  diopters  and  the  quotient  will  be  the  value  in 
the  inch  system.  To  change  from  the  inch  system  to  the  diop- 
tric method  divide  the  number  in  inches  into  40,  and  the  quotient 
will  be  the  corresponding  value  in  diopters.  The  reason  we  use 
40  is  that  the  dioptric  system  is  based  on  the  meter  which  is 
39.37  inches,  and  40  is  so  close  to  this  that  it  is  universally  used. 

AMBLYOPIA. — This  means  poor  vision  due  to  physiologi- 
cal or  pathological  reasons ;  something  wrong  with  the  retina,  the 
optic  nerve  or  the  visual  brain  centers.  It  cannot  be  corrected  by 
lenses  during  the  test. 

EXTERNAL  MUSCLES  OF  THE  EYE.— These  are  six 
in  number,  four  pulling  the  eye  (lightly)  back  against  the  cap- 
sule in  which  it  rests,  and  two  others  acting  with  the  check  liga- 
ments to  pull  the  eye  forward,  thus  keeping  the  organ  in  a  state  of 
equilibrium.  These  muscles  act  harmoniously  together,  so  that  in 
a  normally  functioning  eye  it  may  take  any  position  required  for 
good  vision  with  correctness  and  ease.  Where  this  is  not  the  case, 
then  we  have  a  condition  of  heterophoria  or  muscle  imbalance 
which  may  result  in  headaches,  eyeaches  or  other  disagreable 
symptoms ;  or  else  the  eye  may  give  up  the  struggle  and  squint. 
Heterophoria  is  difficult  to  treat ;  prisms,  muscle  exercises  and 
operations  being  the  means  used. 

ASTHENOPIA.— This  may  be  of  two  kinds,  muscular  or 
accommodative.  In  the  first  case  there  is  strain  on  the  external 
muscles  of  the  eye ;  in  the  latter  it  is  strain  upon  the  ciliary  muscle. 
In  either  case  the  symptoms  are  about  the  same ;  eyeache,  diffi- 
culties with  vision,  and  sometimes  nervous  aflfections,  more  or 


18  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

less  hard  to  discover  and  cure,  whose  connection  with  the  eyes  is 
hard  to  trace.  Usually  lenses  and  cylinders  properly  applied  in 
spectacles  will  correct  accommodative  asthenopia,  while  for  the 
muscular  form  we  must  have  recourse  to  prisms,  muscle  exercises, 
or  even  operations. 

PHOTOPHOBLA. — This  is  an  intolerance  of  light,  more  or 
less  pronounced.  It  may  be  due  to  sluggishness  of  the  iris,  undue 
sensitiveness  or  inflammation  of  the  retina,  and  is  common  in  al- 
binos, or  where  the  eyes  have  been  subjected  to  a  dazzling  light, 
as  well  as  in  diseased  conditions.  It  is  properly  a  case  for  the 
oculist,  though  tinted  glasses  are  sometimes  prescribed  by  the  op- 
tometrist to  rest  the  retina.  Only  smoked  glasses  should  be  pre- 
scribed for  this  purpose. 


CHAPTER   II. 

TESTING  AND  MEANS  EMPLOYED. 

METHODS  OF  TESTING.— There  are  two  general 
methods  of  testing  eyes,  the  subjective  and  the  objective.  In  the 
former  we  depend  upon  what  the  patient  says  in  response  to  our 
questions  as  we  apply  our  various  tests.  In  the  latter  we  judge 
for  ourselves  by  what  we  actually  see.  Both  methods  have  their 
place  in  optometry,  but  the  subjective  test  with  the  trial  case  is  al- 
ways the  court  of  last  resort,  and  everything  is  checked  up  by  it. 

TEST  TYPE  FOR  DISTANCE.— Twenty  feet  has  come  to 
be  the  standard  distance  for  testing  eyes  for  all  uses  except  near 
work.  The  rays  of  light  coming  from  this  distance  are  so  nearly 
parallel  that  the  slight  error  is  disregarded.  The  letters  on  the 
chart  are  usually  black  on  a  white  ground,  and  figured  for  defin- 
ite distances,  the  distance  for  which  the  different  sizes  are  calcu- 
lated being  marked  above  each  line.  These  types  may  be  tised  at 
less  than  the  regular  distance  of  twenty  feet,  but  in  this  case  al- 
lowance must  be  made  for  the  decrease  in  distance.  With  these 
types  we  are  able  to  express  the  visual  acuity  either  with  lenses 
or  without.  In  doing  this  wx  make  use  of  the  fractional  method, 
the  numerator  being  the  distance  of  the  type  and  the  denominator 
the  size.  A  child,  corrected,  if  necessary,  with  lenses,  should 
have  a  visual  acuity  of  20/15;  an  adult  under  the  same  circum- 
stances 20/20;  an  elderly  person  15/20.  Where  this  result  can- 
not be  reached,  the  eye  is  below  normal.     Sometimes  a  better  re- 


20 


THE    TRIAL    CASE    AND    HOW    TO    USE    IT 


suit  can  be  obtained,  and  in  this  case  the  eye  is  above  normal,  but 
these  cases  are  somewhat  rare. 

TEST  TYPE  FOR  NEAR.— There  are  two  varieties  of  this 
type,  one  Jaeger's,  which  is  nothing  more  than  ordinary  type  from 
the  printer's  font  graded  from  the  very  finest  up.  and  the  other 
Snellen's,  which  is  similar  to  the  distance  type,  but  decreased  pro- 


Ul 

E 

3  III 

T  B 

E  Ul  3 

D  L  N 

E  a  Ul  m 

P  T  E  B 

UISEniA 

rSBIlI! 

OIKITQ 

- 

Fi 

(i.  4. — Test  Tyin 

'S. 

portionately  in  size  to  correspond  with  the  short  distances  at  which 
it  is  used.  With  this  type  we  find  the  reading  point  and  the  acuity 
of  vision  for  a  short  distance.  Normal  eyes  should  read  the  very 
finest  type  on  the  chart  at  a  distance  of  13  inches.  Many  eyes  can 
do  even  better  than  this  when  pro{)crly  corrected  with  glasses. 
This  chart  may  also  be  used  in  finding  tlie  amplitude  of  the  ac- 
commodation. 


TESTING     AND    MEANS    EMPLOYED. 


21 


CLOCK  DIAL  CHART.— This  consists  of  a  scries  of  radiat- 
ing lines  with  outer  circles  and  Roman  numbers  arranged  to  cor- 
respond closely  with  the  dial  of  a  clock.  It  is  used  in  connection 
with  cylinders  for  the  detection  and  correction  of  astigmatism. 


Fig.  5.— Clock  Dial  Chart. 


The  Roman  figures  are  used  to  name  the  radiating  lines,  those 
which  are  vertical  being  called  the  XII  to  VI  lines ;  those  which 
are  horizontal  being  called  the  lines  from  IX  to  III,  etc.  The 
values  of  the  lines  are  sometimes  also  read  off  in  degrees ;  the  IX 


A 


Fig.  6. — Types  of  Lenses. 


being  zero,  X  30,  XI  60,  XII  90,  I  120,  II  150,  and  III  180.  This 
numbering  is  in  the  contrary  direction  from  that  of  the  trial  frame, 
but  this  is  necessary  to  make  the  two  agree,  since  they  are  used 
facing  in  different  directions.  There  are  many  other  line-tests 
for  astigmatism,  but  they  are  all  based  on  the  same  principle. 


22 


THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 


PLUS  LENSES. — These  are  magnifying^  glasses.  They 
converge  the  rays  of  Hght,  and  if  the  object  is  far  enough  away, 
they  will  bring  all  the  rays  of  light  from  this  object  to  a  focus, 
where  they  will  form  an  image,  a  duplicate  of  the  object  in  form 
and  color,  but  inverted.  In  the  trial  case  there  are  many  of  these 
plus  lenses  arranged  on  the  dioptric  system  and  graded  from  the 
weakest  to  the  strongest.  Their  values  are  marked  on  the  handles, 
the  fact  that  they  are  plus  being  shown  by  a  cross  stamped  in  the 
metal. 

MINUS  LENSES. — These  are  minifying  glasses.  They  di- 
verge the  rays  of  light,  and  do  not  form  an  image  of  the  illu- 


FiG.  7. — Cylinders. 


minated  object,  no  matter  how  near  or  far  away  it  may  be.  These 
lenses  are  arranged  in  the  trial  case  in  the  same  way  as  the  plus 
lenses,  their  handles  being  usually  stamped  with  a  minus,  and  also 
gilded. 


TESTING    AND     MRANS     EMPLOYED.  23 

CYLINDERS. — These  are  glasses  which  arc  ground  in  one 
direction  only.  Look  at  the  chimney  of  an  argand  gas  lamp  which 
is  cylindrical.  The  outer  surface  of  this  will  show  the  curved  sur- 
face of  a  plus  cylinder,  while  the  inner  surface  will  show  the 
curved  surface  of  a  minus  cylinder.  One  of  the  surfaces  of 
the  cylinders  of  the  trial  case  is  piano.  These  cylindrical  lenses 
are  marked  on  their  handles  in  the  same  way  as  the  plus  and 
minus  spherical  lenses,  but  in  addition  their  surface  for  a  short 
distance  near  the  periphery,  and  parallel  to  the  direction  in  w^hich 
there  is  no  curvature,  is  frosted.  This  shows  the  direction  of  the 
axis  of  the  cylinder.  Referring  again  to  th^  argand  burner  chim- 
ney, the  axis  corresponds  with  the  long  way  of  the  chimney. 


Fig.    8. — rrisms. 


PRISMS. — These  are  wedges  of  glass  which  have  neither 
magnifying  nor  minifying  power,  their  two  surfaces  being  plane. 
Rays  of  light  in  passing  through  a  prism  are  bent  tow^ards  the 
thickest  part  of  the  w^dge,  called  the  base,  the  thicker  the  wedge 


24  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

the  more  the  bending,  while  the  eye  looking  through  a  prism  in 
order  to  see  an  object  in  any  selected  direction  must  turn  from  the 
direct  line  of  sight  towards  the  sharp  edge,  or  apex,  of  the  prism. 
Under  these  circumstances  the  eye  is  looking  around  an  angle. 
Prisms  are  usually  marked  with  a  figure  follow^ed  by  a  little  tri- 
angle to  show  the  number  of  degrees  of  arc  between  the  two  sur- 
faces of  the  wedge.  There  are  other  ways  of  marking  prisms, 
called  the  prism  diopter  and  centrad.  They  are  both  scientific  in 
theory,  but  are  not  in  common  use.  They  will  not  be  discussed 
here.  In  many  cases  there  are  both  circular  and  square  prisms  in 
the  trial  case,  the  former  to  be  used  with  the  trial  frame  and  the 
latter  with  the  fingers. 

OPAQUE  DISC. — This  is  a  solid  piece  of  metal  or  rubber, 
circular  in  form,  to  fit  the  trial  frame.  It  is  used  to  shut  ofif  one 
eye  while  the  other  is  being  tested.  All  modern  optometry  is 
based  on  testing  each  eye  separately,  and  while  this  is  being  done 
the  other  eye  should  remain  open  so  as  not  to  tire  out  the  patient. 
The  opaque  disc  produces  this  result. 

GROUND  GLASS  DISC.— This  is  used  for  the  same  pur- 
pose as  the  opaque  disc,  but  the  operator  can  see  the  eye  through 
the  outside,  which  in  certain  cases  is  an  advantage. 

PIN-HOLE  DISC. — This  is  the  same  as  the  opaque  disc, 
but  with  one  modification.  Its  center  is  pierced  with  a  very  fine 
hole  through  which  the  patient  must  look.  It  has  the  same  efifect 
as  cutting  down  the  size  of  the  pupil  and  this  results,  in  cases 
of  ametropia,  in  reducing  the  circles  of  diffusion  formed  on  the 
retina,  with  the  result  that  the  outlines  of  the  object  looked  at 
become  much  clearer.     It  is  true  that  at  the  same  time  there  is 


TESTING    AND     MEANS    EMPLOYED.  2r. 

much  loss  of  light,  due  to  the  smallness  of  the  hole,  but  the  clear- 
ness of  form  attained  more  than  offsets  this.  Any  eye  that  can  be 
improved  by  this  test  can  always  be  improved  by  lenses.  There 
is  no  exception  to  the  rule. 

STENOPEIC  DISC— This  is  an  opaque  disc  in  tne  center 
of  which  there  is  cut  a  narrow  slit.  With  it  we  can  test  any 
meridian  of  the  eye.  It  is  used  in  some  cases  to  detect  and  cor- 
rect astigmatism.  It  has  one  objection;  the  size  of  the  pupil  of 
the  eye  varies  with  the  amount  of  light  which  passes  through  it 


Fig.  0. — Pin-hole  Disc  and  Stenopeic  Slit. 

to  the  retina.  Since  the  stenopeic  slit  cuts  off  a  large  part  of  tne 
light,  the  pupil  will  dilate  unduly  and  the  peripheral  part  of  the 
lens  will  come  into  play.  As  this  peripheral  portion  is  sometimes 
of  a  different  power  from  the  center,  a  false  finding  may  be  the 
result. 

MADDOX   ROD.— This   is   used   to   uncover  heterophoria. 
It  consists  of  a  glass  rod  attached  parallel  and  in  front  of  a  sten- 


26  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

opeic  slit.  The  small  glass  rod  acts  as  a  strong  cylinder,  thus 
causing  a  light,  such  as  a  candle,  to  appear  as  a  long  streak  about 
the  width  of  the  flame.  The  difference  in  the  appearance  of  this 
from  the  candle  flame  itself  deceives  the  eye,  and  if  there  is  a  ten- 


FlG 


Multiple  ISIaddox   Rod. 


dency  to  heterophoria  the  weak  muscle  will  take  a  position  of  com- 
fort, since  the  mind  fails  to  realize  that  the  two  bright  objects,  as 
seen  by  the  two  eyes,  one  with  the  rod  in  front  of  it  and  the  other 
not,  are  one  and  the  same,  hence  the  fusion  sense  is  not  in  play. 


DOUBLE  PRISM. — This  is  a  solid  piece  of  glass  made  in 
the  form  of  two  prisms,  base  to  base.  It  is  placed  over  the  eye 
so  that  one-half  of  the  pupil  is  behind  one  prism  and  the  othtr  half 
behind  the  other  prism.  This  causes  the  eye  to  see  the  light 
double.  By  using  a  red  glass  over  the  other  eye,  or  even  without 
any  such  glass,  the  patient  will  see  three  lights,  the  upper  and 
lower  ones  being  the  two  images  on  one  retina,  caused  by  the 
double  prism,  and  the  central  one  coming  from  the  other  eye. 
The  result  here  is  the  same  as  with  the  Maddox  rod.  The  eye  is 
deceived  and  the  muscles  take  a  position  of  comfort.     The  po- 


TESTING    AND    MEANS    EMPLOYED.  27 

sition  which  the  central  Hght  seems  to  take  with  relation  to  the 
outer  ones  is  the  measure  of  the  heterophoria,  if  such  exist. 


> 


Fig.   11.— Double  Prism. 

TINTED  PLANOS. — These  are  graded  as  to  the  obscurity 
of  the  tint,  and  have  been  used  as  sufficient  in  cases  of  photo- 
phobia, but  this  practice  is  decreasing,  since  photophobia  has  come 
to  be  looked  upon  as  rather  a  serious  symptom.  Where  the  optom- 
etrist does  prescribe  them,  the  tints  should  be  "smoke,"  no  colors, 
as  the  latter  are  bad  for  the  eyes.  It  seems  to  be  necessary  for 
the  proper  functioning  of  the  retina  that  it  should  receive  white 
light ;  that  none  of  the  spectrum  colors  should  be  missing.  Colored 
glass  cuts  off  some  of  these  colors,  smoke  tint  does  not,  only  de- 
creasing the  amount  of  each  color  entering  the  eye. 

PLANO  LENSES.— There  is  little  call  for  these  in  opto- 
metrical  practice,  but  sometimes  they  are  used  to  detect  maling- 
erers; for  instance,  children  who  want  glasses  just  for  looks. 
These  pianos  are  also  used  in  testing  eyes  of  marked  acuity,  where 
a  lens  which  is  correct  will  seem  to  be  not  as  good  as  the  naked 


28  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

eye  because  the  glass  absorbs  some  of  the  hght  and  therefore 
makes  the  test  card  apparently  not  so  clear.  In  these  cases  when 
a  lens  is  tried  it  must  be  used  in  conjunction  with  a  piano,  so  that 
conditions  of  illumination  of  retina  may  be  equal. 

COLORED  GLASS  DISCS.— These  are  generally  red  and 
green.  Either  may  be  used  in  the  Maddox  rod  test  and  the  two 
can  be  used  together  in  the  FRIEND  test  for  malingerers.  In 
cases  of  marked  hyperphorias  the  colored  glass  discs  alone,  the  red 
or  the  green,  over  one  eye  will  be  sufficient  to  show  that  the  con- 
dition exists,  though  the  Maddox  rod  is  the  best  in  routine  prac- 
tice for  this  purpose. 

COBALT  BLUE  GLASS.— This  is  a  special  test  based  on 
the  supposition  that  if  the  rays  of  light  from  a  source  of  illumina- 


FiG.  12.— Cobalt  Blue  Glass. 


tion  are  cut  down  to  the  red  and  the  blue,  the  accommodation  will 
relax  and  thereby  permit  the  ocular  condition  to  be  diagnosed  by 
the  appearance  of  the  light.  The  glass  used  for  the  purpose  is 
apparently  blue,  but  really  allows  both  red  and  blue  to  freely  pass 


TESTING    AND    MEANS     EMPLOYED.  29 

while  all  the  other  colors  are  almost  entirely  cut  off.  Since  red 
and  blue  are  unequally  refrangible,  there  will  be  two  images  of 
the  flame  formed,  one  blue  and  the  other  red,  the  blue  being  nearer 
to  the  crystalline  lens.  If  the  retina  of  the  eye  corresponds  with 
the  focus  of  the  blue  rays  then  there  will  be  a  clear  blue  image  on 
which  is  superimposed  the  red  image,  but  diffused.  This  will  give 
the  appearance  of  a  blue  center  with  a  red  border.  The  contrary 
will  be  the  case  if  the  retina  corresponds  with  the  focus  of  the  red 
rays,  while  for  an  intermediate  point  the  two  images  will  both  be 
slightly  diffuse  and  will  coincide  in  size.  By  these  different  ap- 
pearances of  the  two  colors  the  refraction  of  the  eye  is  known. 
Astigmatism  is  knowai  by  the  change  in  the  shapes  of  the  two 
colors.  This  test  is  perfectly  reliable  where  there  is  no  accommo- 
dation, but  otherwise  is  more  or  less  uncertain. 

SCHEINER'S  TEST.— This  is  a  very  old  test.  It  consists 
of  an  opaque  disc  pierced  by  two  very  small  holes  close  together. 
The  eye  under  test  must  look  through  both  holes  at  the  same  time, 
the  light  used  being  small  and  bright.  The  appearance  of  this 
light,  sometimes  single,  sometimes  double,  will  give  the  refraction 
of  the  eye.  The  test  is  moderately  reliable,  but  difficult  to  apply, 
as  it  is  not  alw^iys  certain  that  the  patient  is  looking  through  both 
holes  at  the  same  time,  and  this  is  necessary  for  the  success  of  the 
test. 

TRIAL  FRAME.— This  is  a  pair  of  spectacles  made  espe- 
cially for  testing.  By  suitable  adjustments  it  may  be  made  to  fit 
any  eve,  and  by  its  calibration,  if  this  is  correct,  the  size  of  the 
spectacles  to  be  worn  can  be  read  oft*.  It  contains  over  each  eye 
two  or  three  "cells"  or  receptacles  for  holding  the  lenses  and  vari- 


30 


THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 


oils  tests  from  the  trial  case,  one  or  more  of  these  cells  being"  so  ar- 
ranged that  the  lens  or  test  placed  in  it  may  be  revolved.     This  is 


Fig.  13. — Scheiner's  Test. 
Trial  Frame. 


Fig.  14. — Measuring  Card. 


TESTING     AND     MEANS     EMPLOYED.  31 

especially  for  cylinders.  On  account  of  the  weight  of  the  trial 
frame  it  is  an  instrument  of  torture  for  many  people,  and  its  use  in 
these  case  must  be  cut  down  to  the  smallest  space  of  time  pos- 
sible. It  does  not  usually  give  satisfaction  in  taking  facial  meas- 
urements, due  to  errors  in  the  calibration,  to  loose  joints,  and  to 
the  fact  that  very  often  the  round  trial  frame  case  lenses  cannot  be 
put  in  the  same  position  that  the  lenses  of  the  spectacles  or  eye- 
glasses are  to  occupy.  Facial  measurements  are  usually  and  pref- 
erably taken  with  a  small  ruler  divided  into  millimeters  on  one 
edge  and  thirty-seconds  of  an  inch  on  the  other. 


CHAPTER  III. 
THE  CONTENTS  OF  THE  CASE. 

The  complete  trial  case  for  optometrical  work  usually  con- 
sists of  the  following :  A  graded  assortment  of  bi-convex  and  bi- 
concave spherical  lenses  of  from  0.12  diopters  to  20  diopters;  a 
similar  assortment  in  plus  and  minus  cylinders :  a  graded  set  of 
prisms,  both  circular  and  square,  marked  by  their  apex  angles,  of 
from  0.12  to  20  degrees  or  more;  a  three-cell  trial  frame;  and  the 
following  special  testing  discs  :  piano  lens,  tinted  piano  lenses,  Nos. 
I  to  6;  ground  glass  disc,  opaque  disc,  pin-hole  disc,  stenopeic 
disc,  red  glass,  green  glass,  cobalt  blue  glass,  Maddox  rod  and 
double  prism,  the  latter  for  muscle  tests.  Sometimes  there  are 
special  discs,  such  as  Scheiner's  and  the  cone  prism  test.  Such  a 
case  will  cost  $75.00  or  more. 

At  the  other  end  of  the  scale  we  find  the  pocket  case.  This 
contains  a  limited  number  of  lenses  and  discs,  varying  somewhat 
with  the  dififerent  dealers,  but  the  following  will  be  found  to  be  a 
good  selection :  plus  and  minus  spheres  in  pairs,  sizes  0.25,  0.50, 
0.75,  I.,  1.50,  2.,  2.50,  3.,  and  4  diopters;  minus  cylinders  in  pairs, 
.25,  .50,  I.,  1.50,  2.25  and  3  diopters;  five  testing  discs;  ground 
glass,  pin-hole,  stenopeic  slit,  Maddox  rod  and  red  glass.  With 
this  outfit  and  a  plain  three-celled  trial  frame,  ninety  per  cent,  or 
more  of  all  cases  may  be  fitted  provided  the  optometrist  is  a  good 
mathematician,  since  combinations  with  so  limited  an  assortment 
will  usually  have  to  be  figured.  Such  a  pocket  case  may  be  pur- 
chased, including  the  plain  three-cell  trial  frame,  for  about  $15.00. 


THE    CONTENTS    OF    THE    CASE. 


33 


By  adding  to  the  outfit  a  few  high  power  spheres,  plus  and  minus, 
the  percentage  of  cases  which  may  be  treated  will  be  still  higher. 
Between  the  two  extremes  above  mentioned  there  are  all 
grades  of  trial  cases,  at  all  sorts  of  intermediate  prices.  Each  one 
must  decide  for  himself  just  how  far  he  can  go,  bearing  in  mind 


Fig.  15. — Trial  Case. 


always  that  the  more  complete  the  trial  case  the  more  professional 
it  will  seem,  and  the  less  the  optometrist  will  have  to  make  mathe- 
matical calculations. 

The  method  of  trial  case  routine  in  this  work  will  be  so  pre- 
sented that  the  tests  may  be  made  with  any  variety  of  outfit  within 
the  limits  of  price  stated. 


34 


THE   TRIAL    CASE   AND    HOW    TO    USE    IT. 


TEST  CARDS. 

To  properly  meet  all  emergencies,  the  assortment  of  test  cards 
should  be  as  complete  and  varied  as  possible.  There  ought  to  be 
one  or  more  of  Snellen's  distance  test  cards,  each  lettered  differ- 
ently from  the  others,  and  if  possible  a  special  form  of  this  chart 
in  which  the  letters  on  each  line  are  of  decreasing  size.     Also 

n 


m 

tl  jC   Jtt 

^0  r  jtr  jc 

u  i  t  w  fe 

1     galctg 

J        .p.r^M 

lu  a  E  PI  n 


Fig.   16. — Test  Types. 

there  should  be  a  Snellen's  test  card  for  distance  in  German  let- 
ters; the  E  illiterate  chart;  the  picture  chart  for  young  children, 
and  the  clock  dial  and  other  astigmatic  charts.  For  reading  dis- 
tance there  should  be  the  Jaeger  or  the  Snellen  near  chart.  For 
testing  the  ocular  muscles  for  close  work  there  should  be  the  red 
and  black  Maddox  near  test,  to  be  used  with  a  single  prism.     This 


THE    CONTENTS    OF    THE    CASE.  35 

latter  chart  is  figured  for  a  distance  of  lo  inches,  and  it  would  be 
well  to  also  have  one  figured  for  i6  inches.  For  taking  facial 
measurements  there  should  be  either  a  properly  marked  ruler,  or 
else  some  of  the  special  devises  used  for  this  purpose  and  to  be 
had  of  the  various  dealers,  or  possibly,  what  is  better  still,  a  set  of 
sample  frames  containing  piano  lenses  and  marked  with  a  scratch 
to  show  their  geometrical  centers.     For  measuring  out  the  glasses 


B    &    % 

#  Jit  li  e 

«   1^  o   • 


•r     V      ♦      t      0 

Fig.  17.— Test  Types  for  Little  Children. 

on  their  return  from  the  prescription  house  a  protractor  card,  and 
for  quick  w^ork  a  lens  measure,  are  also  needed. 

The  optometrist  who  must  limit  his  purchases  in  these  direc- 
tions can  get  along,  if  he  has  to,  with  the  distance  letter  chart,  a 
near  chart  and  the  clock  dial  chart. 

The  usual  distance  at  which  trial  case  tests  are  made  is  sup- 
posed to  be  20  feet.  This  distance  is  often  stated  to  be  the  same 
practically  as  infinity,  so  far  as  fitting  glasses  is  concerned.  This 
is  not  correct.     If  an  eye  is  fitted  exactly  for  an  infinite  distance, 


36  THE   TRIAL    CASE    AND    HOW    TO    USE    IT. 

such  as  a  brig-ht  star,  by  a  chart  at  a  distance  of  20  feet  it  is  mis- 
fitted to  the  extent  of  about  1-6  of  a  diopter,  so  that  it  will  some- 
times be  found  necessary  to  allow  the  nearest  to  this  in  the  trial 
case,  which  is  1-8  D.  Then  again  it  is  not  always  possible  to  get 
20  feet  of  space.  In  this  case  the  optometrist  must  get  along  with 
less,  but  should  never  forget  that  in  the  prescription  a  suitable 
dioptric  allowance  is  to  be  made  to  make  the  correction  ri^ht  for 

^^       f\      "t// 

d^  V  a 
^^^  ^^"^^  iA\ 

Fig.  18. — Pray's  Astigmatic  Letter  Chart. 

infinity,  the  same  to  be  in  the  form  of  an  increase  for  minus 
glasses  and  a  decrease  for  plus.  Where  the  distance  is  ten  feet 
or  a  little  less  a  good  plan  is  to  use  the  reversed  letter  charts  with 
a  mirror.     These  also  may  be  had  of  all  the  dealers. 

The  distance  letter  charts  should  be  brightly  illuminated. 
There  is  a  rather  general  belief  that  the  chart  should  receive  only 
moderate  illumination,  so  that  it  may  correspond  more  closely 


THE    CONTENTS    OF    THE    CASE. 


37. 


with  natural,  cvcry-day  conditions.  This  sccnis  plausihlc  enough, 
and  yet  there  is  no  logic  in  it.  In  the  first  place,  there  is  no  stand- 
ard of  every-day  illumination,  and,  secondly,  what  we  are  pri- 
marily seeking  to  do  is  to  find  the  dioptric  condition  of  the  eye, 
and  this  can  be  best  done  by  bright  illumination,  the  brighter  the 
better  within  reasonable  limits,  that  is,  within  the  dazzling  point. 
The  light  which  shines  upon  the  distant  reading  charts  should  be 
shaded  so  that  the  eye  of  the  patient  may  receive  little  light,  and 
this  light  should  also  be  arranged,  as  a  matter  of  convenience,  so 


Fig.  19. — Fan  Chart  for  Astigmatism. 

that  the  screen  in  front  of  it  may  be  removed  and  the  light  itself 
used  for  testing  muscle  imbalance,  if  so  desired.  The  trial  case 
also  should  be  sufficiently  illuminated  so  that  the  numbers  and 
marks  on  the  handles  of  the  lenses  may  be  easily  read.  To  see  the 
scale  of  degrees  on  the  trial  frame  there  should  either  be  a  hang- 
ing electric  light,  which  could  be  readily  swung  into  position,  or 
else  a  mirror  could  be  used  to  reflect  the  light  to  the  desired  point. 
The  astigmatic  clock  dial,  as  well  as  all  other  tests  for  astigmatism, 
when  used,  should  be  exactly  at  right  angles  to  the  line  of  sight. 
Where  the  charts  are  movable  and  so  arranged  that  they  can  be 


38  THE   TRIAL    CASE   AND    HOW    TO    USE    IT. 

brought  ill  and  uiit  (jf  sight  fruin  hchiiul  a  scivcii,  there  should  be 
counterweighted  cords  running  across  the  ceihng  and  down  to 
the  optometrist's  hand.  Back  of  the  patient  and  convenient  to 
the  eye  of  the  optometrist  there  should  be  small  cards  which  are 
duplicates  of  the  distant  test  charts,  so  that  he  may  know  whether 
his  patient  is  making  mistakes  or  not,  without  needing  to  turn  and 
look  across  the  room.  When  we  are  testing  a  patient,  we  should 
be  relieved  of  all  possible  inconveniences,  so  we  may  keep  our 
minds  constantly  on  the  test  itself;  and  for  this  reason  it  is 
necessary  to  have  everything  arranged  conveniently.  We  can 
often  make  out  without  all  this  special  preparation  and  arrange- 
ment of  apparatus,  but  we  are  also  liable  at  the  critical  moment  to 
forget  some  little  point  which  may  later  cause  us  considerable 
annoyance,  as  well  as  loss.  To  do  good  work  in  the  refracting 
room,  everything  should  be  arranged  systematically,  and  kept  so. 


CHAPTER  IV. 

THE  PRELIMINARY  TESTS. 

There  are  certain  points,  as  many  of  which  as  possible  ought 
to  be  cleared  up  before  the  optometrist  can  advantageously  begin 
to  apply  his  subjective  tests  with  the  trial  case  apparatus.  These 
will  be  given  here  in  a  routine  order. 

GENERAL  INSPECTION.— In  the  first  place,  the  patient 
should  always  remove  his  or  her  hat,  or  else  the  optometrist  may 
be  put  to  considerable  inconvenience.  This  being  done,  throw  a 
light  on  the  eye  from  the  side.  If  the  eye  is  inflamed,  or  secre- 
tions of  any  kind  are  present,  it  will  be  necessary  to  politely  but 
firmly  refuse  to  take  the  case.  Sore  eyes  are  usually  contagious 
and  some  of  them  are  of  a  very  serious  nature.  In  case  of  slight- 
est doubt,  no  chances  should  be  taken  of  carrying  infection  by 
means  of  the  trial  frame  either  to  the  optometrist  himself  or  suc- 
ceeding patients.  If  no  inflammation  or  secretions  be  present, 
which  will  usually  be  true,  then  the  pupillary  reaction  should  be 
noted.  To  this  end  the  light  should  first  be  pushed  back  so  that 
the  patient's  eyes  are  in  darkness,  and  then  it  should  be  brought 
forward  so  as  to  shine  directly  into  the  eye,  but  a  little  to  one 
side.  The  pupils  of  the  eyes,  under  the  stimulus  of  the  light, 
should  contract  promptly  and  rapidly.  If  there  is  no  contraction, 
or  it  is  very  slow,  the  optometrist  will  often  have  the  reason  at 
once  why  there  are  certain  troublesome  symptoms,  such  as  photo- 
phobia, retinal  fatigue,  and  consequent  nervous  reflexes. 


40  THE    TRIAL   CASE   AND    HOW    TO    USE   IT. 

The  cornea  and  iris  and  adjoining  parts  slionld  now  be  no- 
ticed to  see  if  there  are  any  malformations  present  which  would 
tend  to  reduce  the  visual  acuity,  or,  in  other  words,  normal  vision. 

Some  claim  that  the  shape  of  the  head  and  the  face  will  tell 
the  nature  of  the  optical  imperfection,  but  for  this  the  writer  will 
not  vouch.  He  will  simply  state  here  what  is  claimed  in  this  re- 
gard :  "Flat  face,  hypermetropic  eye ;  long  face,  myopic  eye ; 
non-symmetrical  face,  astigmatism;  large  and  prominent  eyes, 
myopia;  small  eyes,  hypermetropia." 

THE  HISTORY  OF  THE  CASE.— This  is  one.pf  the  most 
important  points.  There  are  some  optometrists  who  consider 
themselves  belittled  if  they  ask  the  patient  any  preliminary  ques- 
tions. They  take  the  ground  that  it  is  their  place  to  find  out  the 
ocular  condition  by  the  use  of  their  optical  appliances  alone.  We 
can  take  a  little  instruction  on  this  point  from  the  physicans. 
Those  of  us  who  are  familiar  with  the  work  of  the  medical  prac- 
titioner and  student  know  how  much  stress  is  laid  on  the  "history 
of  the  case,"  and  how  much  time  is  given  to  it.  There  are  several 
things,  which,  if  possible,  we  should  find  out  by  interrogating  the 
patient. 

Why  does  he  wish  glasses,  and  has  he  ever  worn  them  be- 
fore?    If  so,  for  how  long  and  with  what  results? 

What  particular  ocular  symptoms  does  he  notice?  Is  there 
dimness  of  vision,   either  permanent  or  temporary? 

Does  he  see  double,  and  in  which  direction,  or  do  dark  spots 
ever  seem  to  come  before  his  eyes? 

Does  he  have  hard  work  to  read,  and  does  the  print  ever  seem 
to  dance  or  swim? 

Are  there  headache,  eyeache,  or  burning  sensations  in  the 
eyes,  and  when? 


THE   PREOMINARY   TESTS.  41 

Arc  there  excessive  winking,  or  flow  of  tears,  or  sore-eyes  in 
the  morning? 

Is  a  bright  light  troublesome  ?  Can  he  see  better  at  night  or 
in  the  daytime? 

Has  he  ever  had  eye  disease  of  any  kind,  and  has  any  one  put 
drops  in  his  eye  recently? 

To  ask  categorically  all  of  the  above  questions  would  be  an 
unnecessary  waste  of  time,  but  the  patient  should  be  skillfully  led 
to  give  the  information,  or  as  much  of  it  as  the  inspection  of  the 
eyes  would  seem  to  make  necessary,  though  there  should  be  no 
rambHng  allowed;  this  being  courteously  kept  in  check.  Mean- 
time the  preliminary  tests,  as  here  described,  should  be  going 
on.  Should  the  patient  be  churlish,  we  must  get  what  informa- 
tion we  can.  Still  one  more  point  is  essential,  especially  with 
presbyopes,  and  that  is  to  get  and  measure  out  the  power  of  the 
lenses  previously  worn.  Because  a  patient  has  a  certain  amount 
of  either  presbyopia  or  ametropia,  it  does  not  follow  that  full  cor- 
rection should  be  prescribed.  With  a  knowledge  of  what  the 
patient  has  last  worn,  the  question  of  what  to  have  him  wear  next 
is  more  easily  settled.  When  this  information  cannot  be  had,  we 
may  unknowingly  give  the  patient  what  he  already  has.  This  he 
will  soon  discover  when  he  tries  on  the  new  pair  and  compares 
them  with  the  old  pair  at  home ;  then  he  will  return  to  investigate, 
which  will  not  always  be  pleasant.  To  get  the  strength  of  the 
glasses  which  he  has  previously  been  wearing  is  just  as  necessary 
as  it  is  for  a  physician  to  know  what  medicine  the  patient  has 
previously  been  taking.  It  is  true  that  he  can  often  get  along 
without  the  knowledge,  but  he  will  do  better  with  it.  In  fact,  he 
might  unwittingly  give  his  patient  the  same  old  prescription  with 
the  same  old  taste,  which  he  will  recognize,  with  corresponding 
loss  of  confidence. 


42  THE    TRIAL    CASE   AOT)    HOW    TO    USE   IT. 

LOOKING  IN  THE  EYE  FOR  OPACITIES.— This  is  a 
rapid  test,  mainly  for  the  purpose  of  discovering  if  there  are  any 
signs  of  cataract.  It  is  made  with  the  regular  concave  retino- 
scopic  mirror  at  a  distance  of  about  24  inches  from  the  eye  under 
test.  Let  the  light  be  about  one  meter  distant;  have  the  patient 
look  in  a  little  towards  the  nose ;  nt)w  reflect  the  light  into  his  eye, 
and  the  red  fundus  will  immediately  come  into  view.  If  there  are 
any  opacities  present,  either  corneal,  lenticular  or  in  the  vitreous, 
they  will  appear  as  black  spots  against  the  red  background  of  the 
fundus.  Where  the  observer's  own  eyes  cannot  accommodate  for 
a  distance  of  24  inches,  he  should  attach  such  a  lens  behind  the 
concave  mirror,  as  will  enable  him  to  do  so.  The  object  of  this  is 
to  cut  down  the  corneal  reflex  to  the  smallest  possible  size,  and  this 
will  be  the  case  when  the  observer's  eye  accommodates  properly 
for  this  image;  otherwise  it  will  be  blurred  and  therefore  occupy 
an  increased  space  on  his  retina,  thus  hiding,  perhaps,  some 
opacity. 

Where  the  pupil  of  the  patient's  eye  is  very  small  so  that  the 
fundus  cannot  be  seen  it  will  be  necessary  to  put  a  strong  plus  lens 
in  the  trial  frame. 

THE  COVER  TEST  FOR  HETEROPHORIA.— Direct 
the  patient  to  look  steadily  at  a  small  light  across  the  room.  HoFd 
a  card  before  one  eye  and  watch  it  from  behind  the  card.  Now 
move  the  card  to  cover  the  opposite  eye.  Repeat  in  the  reverse 
direction.  Do  not  be  too  quick  to  make  the  transfer  of  the  card. 
Wait  a  few  seconds  for  the  eye  to  become  fixed.  If,  when  the 
card  is  removed  from  in  front  of  either  eye,  there  is  a  jumping 
movement  of  the  pupil,  then  there  is  heterophoria  present.  Should 
the  cover  test  develop  any  motion  of  this  kind,  then  the  following 


THE    PRFXiMINARY   TESTS.  43 

muscle  test  should  be  made:  Place  over  the  right  e)e  oi  the 
patient  the  Maddox  rod  disc,  and  over  the  left  eye  a  red  glass, 
unless  the  Maddox  rod  is  made  of  red  glass,  when  a  green  glass 
should  be  used  instead.  At  the  opposite  side  of  the  room  have  a 
gas  or  lamp  flame,  in  front  of  which  is  a  screen  pierced  by  a  hole 
one  inch  in  diameter.  Let  the  patient  sit  at  a  distance  from  this 
flame  of  9  feet  6  inches.  Turn  the  test  in  the  trial  frame  until 
the  rod  is  horizontal.  Now  cover  first  one  eye  and  then  the  other 
until  he  has  found  both  lights,  one  being  the  one-inch  flame  col- 
ored green  and  the  other  a  long  streak  of  light.  Take  away  the 
card  altogether  and  he  will  see  the  two  forms  of  light  at  the  same 
timxC,  though  at  first  he  may  have  a  little  trouble  in  this  r-egard, 
but  this  soon  passes.  Now  let  him  describe  to  you  the  relative 
positions  of  the  tw^o  lights ;  how  far  to  one  side  the  streak  is,  and 
on  which  side.  Have  him  express  their  distance  apart  in  terms 
of  the  diameter  of  the  flame.  If  the  distance  from  center  of 
streak  to  center  of  flame  is  one  inch,  the  diameter  of  the  flame, 
then  he  will  have  heterophoria  to  the  extent  that  a  one-degree 
prism  will  correct ;  that  is,  for  every  diameter  of  the  flame  that  the 
centers  of  the  two  lights  are  apart,  there  W'ill  be  required  one  de- 
gree of  prism  to  correct  the  heterophoria.  This  applies,  as  stated, 
to  a  one-inch  flame  at  a  distance  of  9  feet  6  inches.  Make  the 
distance  half  of  this  and  the  flame  would  have  to  be  but  one-half 
inch  in  diameter.  The  optometrist  will  find  that  the  heterophoria 
can  be  discovered  by  this  m.ethod  in  less  time  than  it  has  taken  to 
explain  it.  Every  one  is  familiar  with  an  inch,  and  when  the  pa- 
tient is  told  that  the  flame  is  one  inch  wide,  and  then  asked  how 
many  inches  the  centers  of  the  circle  and  disc  are  apart,  he  will 
answer  correctly. 

With  the  jNIaddox  rod,  as  stated,  over  the  right  eye,  if  the 


44 


THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 


vertical  streak  should  also  he  to  the  rii^ht  of  the  center  of  the  circle 
of  light,  then  there  is  esophoria ;  if  to  the  left,  exophoria.  Now 
turn  the  Maddox  rod  the  other  way,  vertically,  which  makes  the 
streak  of  light  horizontal,  and  test  for  hyperphoria.     The  Mad- 


FiG.    20. — Before   Correction. 


dox  rod  being  still  before  the  right  eye,  if  the  streak  is  above  the 
circle,  then  the  right  eye  looks  down,  or  what  is  the  same  thing, 
the  left  eye  looks  up,  and  we  have  hyperphoria,  while  if  the 
streak  is  below  the  center  of  the  ring  of  light,  then  there  is  right 


THE  PRELIMINARY  TESTS.  45 

hyperphoria.  The  method  of  making  one  inch  at  a  distance  of 
9  feet  6  inches  correspond  to  a  one-degree  prism  (not  a  prism 
diopter)  is  practically  correct  to  20  degrees.  Above  that  there  is 
a  steadily  and  rapidly  increasing  error.     It  is  not  absolutely  nec- 


FiG.  21. — After  Correction. 

essary  to  use  a  green  glass ;  no  glass  at  all  will  do,  but  the  green 
glass  is  easier  on  the  patient's  eyes,  but  where  the  Maddox  rod  is 
white  a  red  glass  over  the  other  eye  may  be  used. 

VISUAL  ACUITY  FOR  DISTANCE.— Visual  acuity  de- 
pends on  several  factors,     "^he  size  of  the  objects  looked  at,  the 


46  THE   TRIAL    CASE    AND    HOW    TO    USE    IT. 

contrast  in  color  between  the  objects  and  their  surroundings;  the 
illumination ;  the  width  of  the  pupil  of  the  observing  eye ;  the  con- 
dition of  the  retina,  the  optic  nerve  and  the  visual  centers  of  the 
brain ;  and  finally  upon  the  perfectness  of  the  eye  as  an  optical 
instrument.  The  standard  used  for  optometrical  work  is  the 
Snellen's  chart  when  under  a  bright  illumination.  This  the  nor- 
mal eye  should  see  distinctly  at  the  distances  as  marked  on  the 
chart.  The  patient  should  be  directed  to  look  at  the  letters  and  to 
read  down  as  far  as  he  can  with  both  eyes,  and  then  with  each  eye 
singly.  A  record  is  to  be  made  of  the  result  for  future  compari- 
son. This  is  with  the  naked  eye.  In  making  this  record  the  fol- 
lowing method  is  used :  express  the  visual  acuity  as  a  fraction, 
the  numerator  being  the  number  of  feet  which  the  patient  is  dis- 
tant from  the  chart  and  the  denominator  being  the  number  of  the 
type.  20/20  means  that  20- foot  type  can  be  read  at  20  feet ; 
10/15  that  15-foot  type  can  be  read  at  10  feet  only;  20/60  partly, 
means  that  part  of  the  60-foot  type  could  be  read  at  20  feet,  but 
not  all  the  letters.  In  using  the  test  letter  chart  it  will  be  noticed 
that  some  letters  are  easier  to  distinguish  than  others.  The  Snellen 
chart  has  its  letters  all  drawn  to  scale,  the  various  parts  of  the  let- 
ters being  one  minute  of  arc  wide,  and  the  letter  as  a  whole  occu- 
pying" 5  niinutes  of  arc.  This  is  the  size  which  a  normal  eye  is 
supposed  to  be  just  able  to  make  out.  The  letter  O  is,  however, 
much  more  readily  distinguished,  3  minutes  of  arc  usually  being 
sufficient,  while  the  letter  L  can  often  be  made  out  with  2  minutes 
of  arc.  Then,  again,  young  people  as  a  rule  will  see  better  than 
normal,  say  20/15,  while  aged  persons  can  rarely  do  better  than 
15/20.  Where  these  visual  acuities  are  reached  it  is  sometimes 
assumed  that  there  is  neither  myopia  nor  astigmatism  present,  un- 
less there  should  also  be  present  eyestrain  or  other  nervous  reflex 
symptom. 


THE   PRELIMINARY   TESTS.  47 

VISUAL  ACUITY  FOR  CLOSE  WORK.— This  test 
should  be  made  with  the  near  type,  either  the  Jaeger  or  Snellen. 
The  patient  should  be  allowed  to  hold  the  printed  matter  at  any 
distance  he  chooses,  and  the  record  should  show  this  distance  as 
well  as  the  smallest  size  of  type  that  he  can  read.  The  two  eyes 
should  be  tested  together  first  and  then  each  eye  separately. 
Records  can  be  made  similar  to  the  following :  No.  I  at  20 
mchcs ;  No.  7  at  8  inches,  etc.  It  would,  of  course,  be  better  to 
use  the  same  notation  as  with  the  distance  chart,  but  usually  the 
near  test  charts  are  not  marked  on  the  Snellen  basis. 

THE  FAR  POINT  IN  MYOPIC  EYES.— Hold  the  near 
type  at  a  distance  of  six  feet  or  so  from  the  patient  and  then  draw 
gradually  nearer  until  the  letters  come  clear.  If  at  the  distance  of 
six  feet  the  letters  are  blurred,  but  come  out  clear  when  the  chart 
is  brought  nearer,  then  there  is  myopia  present,  and  the  point  at 
which  the  letters  are  first  clear  is  the  far  point  for  that  particular 
eye. 

TO  FIND  THE  NEAR  POINT  IN  ALL  EYES  NOT 
TOO  HYPEROPIC— This  is  found  in  the  same  way  as  in  the 
previous  paragraph,  excepting  that  the  chart  is  brought  farther 
forward,  until  the  letters  begin  to  blur  again.  Where  the  eyes 
are  myopic  this  will  give  us  both  the  far  and  near  point;  the  far 
point  when  the  letters  come  clear  and  the  near  point  when  they 
begin  to  blur  again.  By  measuring  the  distance  from  the  eye  in 
each  case  and  expressing  the  result  as  diopters,  we  can  get  the 
amplitude  of  accommodation,  which  will  be  the  difference  be- 
Uveen  the  two  values.  Furthermore,  the  far  point  itself,  ex- 
pressed in  diopters,  will  be  the  measure  of  the  myopia.     Where 


48  THE   TRIAL    CASE   AND    HOW    TO   USE   IT. 

the  eye  is  too  hyperopia  and  presbyopic  there  will  be  no  actual 
near  point.  As  a  check  on  the  above  method,  the  following-  may 
be  used :  Hold  the  near  test  chart  close  to  the  eyes  and  gradually 
withdraw  it  The  near  point  will  be  the  point  where  the  type  first 
comes  clear. 

THE  AUTHOR'S  SPECIAL  METHOD  OF  MAKING 
THE  NEAR  TEST. — It  is  not  always  an  easy  matter  to  get  the 
exact  near  point  by  means  of  the  near  reading  chart,  for  the  patient 
is  often  liable  to  read  by  pseudo-accommodation,  the  power  of 
reading  slightly  blurred  images.  Some  patients  will  pronounce 
the  letters  perfectly  clear  when  they  may  be  out  of  focus  as  much 
as  a  whole  diopter.  To  meet  this  difficulty  the  author  has  devised 
a  special  form  of  near  test  which  is  extremely  accurate.  It  con- 
sists of  a  ruler  on  which  there  is  freely  movable  a  cardboard 
slider  containing  three  vertical  targets,  on  each  of  which  are 
drawn  three  fine  black  vertical  lines,  the  distance  between  targets 
being  two  inches,  though  this  distance  may  be  made  less.  To 
use  the  device,  rest  the  ruler  against  the  cheek  bone  under  the 
patient's  eye  and  push  the  slider  up  as  close  to  the  eye  as  it  will 
go.  Usually  the  lines  on  all  three  targets  will  be  blurred ;  if  not 
they  may  be  made  so  by  placing  a  suitable  lens  before  the  eye. 
Next  the  apparatus  should  be  withdrawn  slowly  until  the  lines  on 
the  two  outer  targets  become  perfectly  clear,  while  the  inner  one 
remains  blurred.  The  near  point  will  then  be  marked  by  the 
middle  target  if  the  patient  is  young,  and  by  the  point  midway  be- 
tween the  two  if  he  is  presbyopic. 

THE  PATIENT'S  READING  DISTANCE.— This  does 
not  mean  the  distance  at  which  he  reads  when  he  comes  to  have 


THE   PRELIMINARY   TESTS.  49 

his  eyes  examined,  but  rather  that  point  where  considering  his 
length  of  arm  and  other  anatomical  points,  it  will  be  the  right 
place  for  him  to  read  when  he  takes  an  easy  position.  The  con- 
dition of  his  eyes  after  fitting  will  also  have  something  to  do  with 
it.  It  is  often  assumed  that  the  reading  distance  should  be  ex- 
actly 13  inches,  but  for  the  reasons  above  stated  this  is  not  always 
the  case.  Have  the  patient,  with  a  piece  of  blank  paper  in  his 
hand,  take  that  position  which  is  most  comfortable  for  him. 
Measure  this  distance  from  the  eye,  and  make  a  note  of  the  same. 


CHAPTER  V. 
TESTS  FROM  THE  TRIAL  CASE. 

When  the  preliminary  tests  have  been  completed  the  optom- 
etrist will  usually  have  a  pretty  close  idea  of  the  patient's  ocular 
condition,  and  what  is  left  for  him  to  do  is  to  determine  that  con- 
dition with  accuracy.  To  this  end  he  should  proceed  method- 
ically and  according  to  some  chosen  system.  As  to  what  system 
shall  be  followed  in  routine  cases,  that  is  a  point  on  which  there  is 
apt  to  be  some  difference  of  opinion.  The  method  given  here  is 
the  one  which  the  author  has  found  in  his  own  experience  to  be 
the  most  satisfactory  in  ordinary  cases.  In  the  extraordinary 
ones  he  has  always  been  prepared  to  use  some  other  special  test,* 
whichever  one  seemed  to  best  fit  the  circumstances  of  the  case. 
The  regular  routine,  then,  will  be  as  follows: 


♦Subjective  Tests   for  Difficult   Cases;   Frederick   Boger  Publishing 
Co.,  I  Maiden  Lane,  New  York. 


50  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

ARTIFICIAL  FAR  AND  NEAR  POINT.— If  the  case  is 
one  of  myopia,  as  shown  by  the  tests  already  made,  it  will  not  be 
necessary  to  test  for  the  artificial  far  and  near  point,  since  the  in- 
formation sought  has  already  been  gained.  When  this  is  not  true, 
however,  a  plus  4  diopter  spherical  lens  should  be  placed  in  the 
single  cell  trial  frame  over  the  right  eye.  (As  a  matter  of  routine 
it  is  best  to  always  commence  with  the  right  eye  in  all  tests  and 
examinations.)  The  use  of  the  plus  4  diopter  lens  is  not  only  to 
get  the  artificial  far  point,  but  also  in  cases  of  spasm  of  the  accom- 
modation to  unlock  the  spasm,  which  wdll  take  place  in  a  few 
moments  after  the  lens  has  been  put  in  place.  Now  take  the  read- 
mg  chart,  or  the  author's  special  test,  suitably  illuminated  from  a 
light  from  behind  and  a  little  to  one  side  of  the  patient.  Move 
the  chart  away  from  the  eye  to  be  tested  until  the  letters  on  it  are 
all  a  blur,  and  then  bring  it  gradually  nearer  until  the  print  be- 
comes clear.  This  will  be  the  artificial  far  point  with  a  plus  4 
diopter  lens.  Measure  the  distance  from  the  eyes,  convert  it  into 
the  corresponding  dioptric  value  by  dividing  into  40,  and  sub- 
tract the  result  from  plus  4  diopters.  The  answer  will  be  the 
approximate  correction  for  distant  vision.  When  we  put  a  plus 
4  lens  before  an  emmetropic  eye,  the  far  point  is  brought  from 
infinity  up  to  10  inches  or  less.  If  we  find  with  this  lens  that  the 
artificial  point  is  not  10  inches,  then  the  eye  is  not  emmetropic. 
If  this  far  point  is  at  13  inches,  which  corresponds  to  plus  3 
diopters,  then  to  bring  it  up  the  remaining  distance  to  10  inches, 
or  4  diopters,  we  would  have  to  add  the  difference  between  plus  3 
and  plus  4,  or  plus  i  diopter,  which  is  therefore  the  approximate 
measure  of  the  ametropia.  If,  on  the  contrary,  with  the  plus  4 
diopter  lens  we  find  the  artificial  far  point  to  be  at  9  inches,  which 
corresponds  to  4.50  diopters,  then  the  eye  may  be   .50  diopters 


TESTS   FROM    THE   TRIAL    CASE.  51 

myopic,  though  often  this  will  not  be  true,  since  the  sense  of 
nearness  will  often  induce  a  certain  amount  of  ciliary  spasm. 

After  the  artificial  far  point  has  been  noted,  then  the  read- 
ing chart  would  be  brought  still  nearer  until  it  blurs  again,  this 
time  because  it  has  been  brought  within  the  nearest  point  at  which 
it  can  be  made  out  with  all  of  the  accommodation  in  force ;  by  now 
moving  the  chart  a  little  back  again  the  point  will  be  found  within 
which  the  letters  will  blur.  This  is  the  artificial  near  point  for 
this  particular  eye  with  a  plus  4  diopter  lens.  Note  this  distance 
and  convert  it  into  the  corresponding  diopters  as  before. 

A  large  proportion  of  the  patients  will  have  no  difficulty  in 
making  out  the  smallest  type  on  the  test  chart  both  for  this  arti- 
ficial far  and  near  point,  but  there  will  be  others  who  will  not  be 
able  to  do  this.  Such  a  result  would  argue  amblyopia,  or  astig- 
matism, and  note  should  be  made  accordingly.  To  suit  these 
cases,  attention  should  be  called  to  the  smallest  type  that  can  be 
made  out. 

AMPLITUDE  OF  ACCOMMODATION.— This  is  the  ex- 
tent to  which  the  ciliary  muscle  can  contract  expressed  in  diopters. 
To  find  out  how  much  it  is,  we  deduct  the  far  point  from  the  near 
point  expressed  in  diopters.  For  instance,  if  the  artificial  far 
point  is  found  to  be  at  16  inches  and  the  artificial  near  point  at  5 
inches  from  the  eye,  then  the  amplitude  of  accommodation  for  near 
which  is  usually  a  little  different  than  for  distance  will  be  5>4 
diopters,  for  16  inches  corresponds  to  2J/2  diopters  and  5  inches 
corresponds  to  8  diopters,  and  the  difference  between  the  two  will 
be  as  above  stated.  The  amount  of  the  amplitude  of  accommoda- 
tion will  vary  with  the  individual  and  his  age.  The  table  by  Don- 
ders  as  given  below,  will  apply  to  most  cases,  and  where  the  actual 


I 


52  THE    TRIAL    CASE   AND    HOW    TO    USE   IT. 

amount  in  any  case  as  tested  out  is  less,  then  there  will  be  a  sus- 
picion of  paralysis  of  the  accommodation,  or  spasm  of  accommo- 
dation, or  a  mistake  in  the  age  of  the  patient. 


ears. 

Amplitude  in  D. 

Years. 

Amplitude  in  D. 

lO 

14- 

45 

3-50 

15 

12. 

50 

2.50 

20 

10. 

55 

1.75 

25 

8.50 

60 

I. 

30 

7. 

65 

0.75 

35 

5.50 

70 

0.25 

40 

4-50 

75 

0.00 

DEVELOPMENT  OF  THE  MERIDIAN  OF  GREAT- 
EST POWER. — The  correction  of  astigmatism  is  the  greatest 
difficulty  which  stands  in  the  path  of  the  optometrist.  To  be  cer- 
tain in  this  branch  of  testing  requires  constant  watchfulness. 
There  are  two  theories  as  to  the  way  in  which  an  astigmatic  eye 
sees.  One  is  that  it  accommodates  for  an  intermediate  position 
between  the  two  principal  meridians,  so  as  to  reduce  the  difficulty 
to  a  minimum,  and  undoubtedly  in  some  cases  this  is  true.  The 
other  is  that  the  eye  first  adjusts  for  one  meridian  and  then  for 
the  one  at  right  angles.  This  action  is  assumed  to  be  extremely 
rapid,  the  two  images  being  continually  superimposed.  If  this 
latter  theory  is  correct,  we  have  a  good  explanation  of  two  im- 
portant points ;  one  being  why  so  many  astigmatic  eyes  see  so 
much  better  than  ought  to  be  the  case  as  compared  with  emme- 
tropic eyes,  and  the  other  why  small  errors  of  astigmatism  pro- 
duce in  some  cases  such  marked  eyestrain  and  reflex  symptoms. 
In  any  event,  no  matter  which  theory  is  correct,  one  thing  is  cer- 
tain ;  the  accommodation  is  usually  in  abnormal  play,  and  unless 


TESTS    FROM    THE    TRIAL    CASE. 


53 


^ 


Fig.  22.— An  Adjustable  Outfit. 


54  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

we  force  this  to  relax  we  stand  little  chance  of  getting  the  true 
principal  astigmatic  meridians.  But  this  is  not  all.  Where  the 
meridians  are  oblique  the  prescription  is  apt  only  too  often  to  be 
wrong,  either  because  of  an  error  on  the  part  of  the  optometrist, 
or  because  the  glasses  are  set  wrong  in  the  frame,  usually  the  for- 
mer. A  sphero-cylinder  with  axis  120°  wnll  become  60°  if  turned 
the  wrong  side  out  in  the  frame.  Also  it  is  quite  evident  that  with 
oblique  meridians  it  will  not  do  for  the  spectacle  eyes  to  be  re- 
versed in  the  frames,  since  a  right  lens  with  axis  60°,  for  instance, 
would  not  be  correct  if  put  in  the  left  eye  wire.  To  show  that 
the  optometrist  may  readily  make  an  error  in  the  case  of  oblique 
axes  and  meridians,  let  him  try  the  following  experiment:  Hang 
the  clock  dial  chart  on  the  wall.  On  a  table  on  the  opposite  side 
of  the  room  place  a  trial  frame  just  as  it  would  be  were  it  on  a 
patient's  face,  or  it  may  be  placed  on  some  one's  face.  Now  look 
at  the  clock  dial  and  select  the  lines  from  V  to  XI ;  decide  with 
what  degree  of  the  trial  frame  these  lines  correspond.  Now  take 
a  ruler,  place  it  over  the  lines  from  V  to  XI ;  then  holding  it 
rigidly  in  this  direction,  carry  it  across  the  room  to  the  frame  and 
see  if  it  marks  the  number  of  degrees  decided  upon  at  first  as  cor- 
rect. N^ot  every  one  will  get  it  right,  since  the  lines  from  V  to 
XI  will  be  found  to  correspond  to  60°  and  not  to  120°.  and  the 
lines  from  IV  to  X  will  correspond  to  30°  and  not  to  150°. 

The  first  step,  then,  in  the  correction  of  astigmatism  is  to 
properly  locate  the  principal  meridians,  and  this  cannot  be  done 
with  any  certainty  unless  the  accommodation  is  relaxed  during  the 
test ;  neither  will  the  result  be  attained  the  most  smoothly  unless 
the  patient  receives  first  such  explanation  as  will  give  him  some 
idea  of  what  you  are  trying  to  do. 

Remove  the  plus  4  diopter  lens  from  before  the  patient's  eye 


TESTS    FROM    THE    TRIAL    CASE.  65 

and  let  him  examine  the  clock  dial  chart  in  his  hands.  Call  his 
attention  to  the  fact  that  it  is  arranged  somewhat  like  a  clock. 
Have  him  notice  that  in  each  direction  there  are  three  parallel 
black  lines  with  two  white  spaces  between.  Next  estimate  his 
approximate  correction  for  one  meter.  This  is  obtained  from  the 
artificial  far  point,  as  already  shown.  Put  the  appropriate  lens  in 
the  adjustable  trial  frame,  properly  centered,  turn  the  letter  chart 
to  the  wall,  hang  the  clock  dial  in  position,  so  that  it  is  on  a  level 
with  the  eye  to  be  tested.  Ask  the  patient  if  he  sees  all  the  black 
lines  with  intervening  white  spaces  equally  distinct,  and  if  all  their 
edges  are  sharply  defined.  Do  not  ask  "which  line  is  the  blackest." 
Some  people's  idea  of  a  black  line  takes  into  consideration  not  only 
the  intensity  of  the  blackness^  but  the  retinal  area  of  its  image  as 
well.  Now  increase  the  power  of  the  lenses,  if  plus,  or  decrease 
the  power,  if  minus,  until  all  the  lines  on  the  chart  are  blurred. 
Then  take  the  clock  dial  from  the  wall  and  holding  it  with  the  VI 
to  XII  lines,  exactly  vertical,  steadily  approach  the  patient.  Di- 
rect him  to  tell  you  which  series  of  lines  come  out  clear  the  first. 
These  will  always  show  the  meridian  of  greatest  power,  and  by 
noting  the  point  where  they  become  clear,  while  the  lines  in  the 
other  direction  are  still  blurred,  an  idea  may  be  gained  of  the  re- 
fractive condition  of  the  eye  so  far  as  that  meridian  is  concerned. 
This  is  discovered  by  converting  the  distance  from  the  eye  at 
which  the  first  lines  come  clear  into  diopters,  and  subtracting  the 
same  from  the  power  of  the  lens  which  happens  to  be  in  the  frame. 
Place  the  clock  dial  back  on  the  wall,  and  decrease  the  power 
of  the  lens  in  the  frame  just  enough  if  a  plus;  or  increase  it,  if  a 
minus,  until  the  patient  again  sees  the  lines  of  the  most  defective 
meridian  clearly,  while  all  the  others  are  more  or  less  blurred. 
Now  apply  minus  cylinders  with  axes  at  right  angles  to  the  black- 


56  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

est  line,  which  is  always  the  most  defective  meridian,  until  all 
the  sets  of  radiating  lines  are  alike. 

Should  the  method  of  procedure  as  stated  above  develop  no 
difference  in  the  lines,  then  there  is  no  appreciable  astigmatism  in 
that  particular  eye. 

CHECKING  UP  ON  THE  LETTER  CHART.— Leaving 
all  lenses  in  place,  remove  the  clock  dial,  and  direct  the  patient's 
attention  to  the  letter  chart.  Let  him  read  down  as  far  as  he  can. 
Now  shift  the  axis  of  the  cylinder,  if  the  previous  test  has  shown 
astigmatism,  from  side  to  side,  to  see  if  vision  can  be  improved. 
It  will  sometimes  happen  that  the  axis  is  off  a  few  degrees  and 
this  procedure  will  disclose  the  fact.  Next,  in  cases  of  medium 
and  high  cylindrical  corrections,  call  the  patient's  attention  to  the 
chart  as  a  whole  and  ask  if  it  seems  perfectly  rectangular,  or 
whether  it  appears  slanting.  Shift  the  axis  of  the  cylinder  again 
if  necessary  until  this  appearance  disappears.  The  usual  final  test 
in  cases  of  astigmatism  is  the  ability  to  best  read  the  smallest 
letters  possible  but  where  rectangular  objects  seem  on  the  slant, 
this  must  be  cleared  even  at  the  sacrifice  of  a  little  acuity. 

THE  FINAL  COMPARATIVE  TEST.— The  optometrist 
may  be  sure  that  the  finding  as  above  given  is  the  right  correction 
so  far  as  the  cylinder  is  concerned,  and  a  succession  of  tests  with 
intervening  periods  of  time  will  always,  in  case  of  healthy  eyes, 
give  the  same  result.  It  now  remains,  however,  to  get  the  spheres 
exactly  right.  For  this  we  should  first  change  the  letter  chart,, 
since  by  this  time  many  patients  will  have  memorized  the  letters. 
We  are  to  depend  on  the  sense  of  contrast,  which  is  an  ex- 
tremely   discriminative   ocular    faculty.     Take   in   one   hand   a 


TESTS    FROM    THE    TRIAL    CASE.  57 

piano,  and  in  the  other  a  phis  .50  sphere.  First  hold  the  piano  in 
front  of  the  correction  already  in  place  in  the  frame,  wait  a 
few  seconds,  and  then  substitute  the  plus  50,  and  ask  if  the  latter 
has  caused  a  slight  blur,  making  sure  first,  however,  that  the 
patient  knows  what  you  mean  by  the  word  "blur."  If  the  plus 
50  does  not  blur,  then  take  in  one  hand  a  plus  .50  and  in  the  other 
a  plus  I.  and  repeat  the  test.  Whenever  the  increase  of  .50 
as  stated  above,  produces  a  blur  in  the  chart,  then  the  correction 
which  does  not  blur  is  the  one  desired.  Should  the  plus  .50 
in  the  first  case  blur,  then  try  a  piano  in  comparison  with  a 
minus  .50,  trying  the  latter  first.  If  necessary  compare  a  minus 
I.  and  a  minus  .50  in  the  same  way,  the  minus  i.  to  be  tried 
first.  The  reason  why  a  piano  should  be  used  as  described 
is  that  with  patients  of  sharp  vision  the  chart  will  be  pronounced 
blurred  because  of  a  slight  dimness  caused  by  the  absorption  of 
light  by  the  glass  of  the  lens  itself.  Glass  absorbs  light,  and 
with  very  sharp  eyes  this  fact  should  be  reckoned  with.  The 
point  will  be,  perhaps,  better  realized  by  the  following  experiment : 
Look  first  through  an  open  window  and  then  through  the  win- 
dow glass.  The  difference  will  be  quite  noticeable,  no  matter 
how  well  cleaned  the  window  glass  may  be.  Should  the  test 
as  made  seem  to  show  that  even  with  the  piano  lens  the  patient 
is  confusing  this  dimness  with  blurring,  then  a  tinted  piano  may 
be  used  to  make  sure. 

In  some  cases  it  will  be  possible  to  do  finer  work  than  the 
above;  that  is,  where  the  visual  sharpness  is  unduly  acute,  the 
comparative  test  may  be  made  with  differences  of  .25  D.,  or  even 
in  some  cases  with  .12  D.  On  the  contrary,  where  the  visual  sharp- 
ness is  low,  the  test  may  have  to  be  made  with  differences  of  power 
of  I  D.  or  even  more. 


58  THE   TRIAL    CASE   AND    HOW    TO    USE   IT. 

CHECKING  UP  AT  THIRTEEN  INCHES.— In  cases  of 
doubt  the  following  may  be  added  to  the  above.  Combine  a  plus 
3  with  the  correction  for  distance  already  in  the  frame.  This 
should  make  the  artificial  far  point  at  about  13  inches,  and  if  on 
testing  with  the  near  chart  for  the  artificial  far  point,  this  does 
not  prove  to  be  the  case,  then  something  is  wrong;  either  a  mis- 
take has  been  made,  or  else  latent  hyperopia  has  not  been  all  made 
manifest. 

A  DOUBLE  CHECK  TEST.— When  the  eye  has  been  fitted, 
and  the  full  correction  for  distance  is  still  in  place,  hold  a  plus 
.25  sphere  in  front  of  the  other  lenses  in  the  frame.  The  type 
should  blur  a  little.  Next  w^ith  the  plus  .25  still  in  place  bring 
in  front  of  it  with  the  other  hand  a  minus  .25  sphere.  The  type 
should  come  clear  and  sharp  at  once.  A  plus  and  minus  .50  may 
be  used  in  the  same  way  for  eyes  of  sub-normal  acuity. 

THE  PIN-HOLE  TEST.— Whenever  the  visual  acuity  can- 
not be  brought  up  to  normal  this  test  should  be  used.  With  it 
the  test  letters  will  never  look  so  bright  and  clear,  but  where  the 
subnormal  vision  is  due  to  optical  defects  of  the  eye  alone  the 
patient  will  be  able  to  make  out  smaller  letters  on  the  chart  with 
the  pin-hole  disc  than  without  it.  This  is  due  to  the  fact  that  the 
very  small  hole  in  the  opaque  disc  cuts  down  the  angle  of  aper- 
ture so  much  that  diffusion  circles  on  the  retina  are  made  ex- 
tremely small,  thus  permitting  outlines  to  be  more  easily  fol- 
lowed. Where  subnormal  vision  is  due  to  some  physiological  or 
other  similar  condition,  then  vision  through  the  pin-hole  will  not 
be  improved  but  usually  will  be  made  w^orse.  In  placing  the  pin- 
hole disc  before  the  eye  be  sure  that  it  is  properly  centered  for  the 


TESTS    FROM    THE   TRIAL    CASE.  59 

pupil,  it  will  be  found  mure  satisfactory  with  intellig-ent  patients 
to  have  a  special  holder- with  a  handle  for  the  pin-hole  disc,  so  that 
the  patient  may  adjust  it  for  himself.  Where  the  visual  acute- 
ness  is  very  poor  it  is  a  good  plan  to  use  the  pin-hole  disc  as  the 
very  first  test  so  as  to  get  some  idea  of  the  correction  by  lenses 
as  soon  as  possible. 


CHAPTER  VI. 

TESTS  FROM  THE  TRIAL  CASE  (Continued) 

THE  LENS  PRESCRIPTION.— After  the  dioptric  con- 
dition of  the  eyes  has  been  determined,  the  next  question  is  what 
to  prescribe.  The  rule  followed  by  some  is  very  simple :  Give 
the  full  correction  and  insist  that  the  patient  wear  it  through  thick 
and  thin  until  it  becomes  acceptable  and  comfortable.  This 
method  takes  no  account  of  previous  physiological  habits.  It  is 
based  on  implicit  obedience  on  the  patient's  part  and  often  fails, 
for  the  reason  that  the  average  individual  in  wearing  glasses  will 
reach  a  decision  as  to  their  fitness  at  the  end  of  a  very  short  time, 
long  before  he  has  had  a  chance  to  "get  used  to  them."  In  de- 
ciding this  question  he  has  no  consideration  for  anything  but  his 
own  feelings ;  he  does  not  compare  his  old  visual  acuity  with  his 
new ;  he  forgets  all  about  it ;  but  simply  knows  that  the  glasses  are 
uncomfortable,  which  was  not  the  case  with  the  old  ones,  and 
hence  he  rejects  them  and  visits  some  other  optometrist  who  may 
not  be  so  fixed  in  his  ideas  as  to  the  necessity  of  always  giving 
a  full  correction.     The  scientific  fitting  of  lenses  to  the  eye,  with 


60  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

due  regard  to  acquired  and  natural  ocular  functions,  is  a  delicate 
problem  which  must  be  settled  separately  for  each  case.  The 
points  to  be  known  are  the  dioptric  condition  of  the  eye;  the 
glasses  previously  worn,  if  any,  and  the  rules  of  physiological 
habits.  Especially  is  this  true  in  medium  and  high  defects  and  in 
anisometropia.  In  the  first  place,  with  adults,  when  astigmatism 
requires  only  .50  cylinder  for  correction,  and  there  are  no  trouble- 
some symptoms,  it  will  usually  be  best  to  disregard  the  cylinder 
altogether.  In  the  second  place,  while  no  regular  rule  can  be  laid 
down  to  fit  all  cases,  it  will  be  good  routine  practice  for  the  first 
pair  of  glasses  to  allow  the  eye  muscles  to  do  a  portion  of  the 
work,  and  in  the  succeeding  ones  to  gradually  cut  down  the 
amount  of  this  work  if  the  circumstances  seem  to  require  it. 
Where  one  of  the  eyes  is  amblyopic  it  will  sometimes  be  best  to 
let  one  eye  be  fitted  and  disregard  the  other,  though  recently 
quite  a  movement  has  arisen  to  first  correct  the  best  eye  with 
one  pair  of  glasses  for  ordinary  use,  and  then  by  special  lenses  to 
develop  the  poor  eye,  unless  the  difference  between  them  optically 
be  too  great.  To  this  end  a  special  pair  of  glasses  is  given  in 
which  only  the  poorer  eye  is  corrected ;  these  practice  glasses 
to  be  used  at  regular  intervals,  say  three  times  daily,  the  good 
eye  meantime  being  stopped  off.  Later,  if  the  poor  eye  can  be 
worked  up  to  the  other  in  visual  acuity  with  proper  correction,  a 
pair  of  glasses  is  given  correcting  both  eyes.  Again,  in  cases 
of  anisometropia  the  question  is  whether  to  have  one  eye  for 
reading  and  the  other  for  distance,  or  to  try  to  make  both  eyes 
work  together.  Where  the  difference  between  the  two  eyes  does 
not  exceed  i  D.,  the  latter  method  can  eventually  be  used,  but 
where  the  difference  is  greater  than  i  D.  this  method  will  usually 
prove  impracticable.     In  any  event,  if  the  attempt  is  made  to  get 


TESTS    FROM    THE    TRIAL    CASE.  61 

the  two  eyes  to  work  together  the  first  glasses  prescribed  should 
only  allow  for  one-half  of  the  difference  of  the  two  eyes,  to  be 
followed  later  by  a  correction  with  the  full  difference.  In  each 
case  the  patient  must  wear  the  glasses  constantly,  or  the  method 
will  be  of  no  use.  One  objection  to  fitting  cases  of  anisometropia 
in  this  way  is  that  the  patient  becomes  dependent  on  his  glasses, 
and  if  by  any  mishap  they  are  broken,  he  will  be  put  to  a  great 
deal  of  annoyance  until  they  are  repaired.  In  the  case  of  high 
myopes  it  will  be  found  often  that  the  power  of  accommodation  is 
more  or  less  diminished  from  non-use ;  hence  the  glasses  prescribed 
should  not  throw  the  near  point  out  too  far,  but  the  lenses  should 
be  made  as  strong  as  possible  consistent  with  comfort,  and  the 
patient  should  return  later  for  a  stronger  pair.  Eventually  and 
as  soon  as  possible  the  full  amount  of  the  myopia  should  be  cor- 
rected. This  is  the  consensus  of  opinion  of  most  optometrists 
and  oculists. 

THE  BINOCULAR  TEST  FOR  DISTANCE.— This,  of 
course,  would  be  omitted  in  the  case  of  one-eyed  patients,  of  which 
the  optometrist  will  occasionally  have  a  case.  After  each  eye  has 
been  fitted  separately,  the  binocular  test  should  be  made.  Have 
the  correction  selected  for  distance,  in  accordance  with  the  pre- 
vious paragraph,  in  place.  Let  the  patient  look  at  the  smallest 
letters  on  the  distant  chart  that  he  can  make  out.  Now  with  a 
pair  of  plus  .25  lenses  see  if  the  glasses  will  be  more  acceptable 
with  this  addition;  try  the  same  thing  with  plus  .50  and  with 
minus  .25  and  minus  .50  spheres.  It  will  usually  be  found  that 
there  will  be  no  need  to  make  any  change  where  the  eyes  are 
alike.  Where  this  is  not  true,  however,  whether  because  of  dif- 
ferences in  refractive  power  or  in  the  axes  of  meridians  of  astig- 


62  THE    TRIAL    CASE   AND    HOW    TO    USE    IT. 

matism  or  both,  it  may  be  necessary  to  make  some  changes  in  the 
relative  strength.  For  this  purpose  use  the  lenses  as  given  above, 
also  similar  cylindrical  powers,  not  over  the  two  eyes  together, 
but  over  each  in  turn.  For  instance,  suppose  there  is  aniso- 
metropia of  I  D.,  and  suppose  we  have  decided  to  make  a  differ- 
ence in  the  two  glasses  of  but  .50  D.,  arguing  that  the  eye  muscles 
are  to  be  half  relieved  of  the  discrepancy.  We  may  find  that  we 
will  have  to  cut  the  difference  down  to  .25,  or,  on  the  other  hand, 
we  may  be  able  to  go  up.  Each  individual  case  is  a  law  unto 
itself  in  this  regard. 

GLASSES  FOR  COS^^IETIC  PURPOSES.— These  are 
given  in  the  case  of  the  blind,  either  in  one  eye  or  both,  where  the 
misfortune  is  noticeable.  For  a  person  totally  blind,  blue  or 
smoke  glasses  are  usually  given,  but  ground  glass  lenses  will  be 
less  conspicuous.  In  the  case  of  a  shrunken  eye,  it  is  advisable 
sometimes  to  fit  with  a  strong  glass,  which  by  its  magnifying 
power  will  make  the  two  eyes  look  of  the  same  size. 

READING  LENSES. — The  usual  method  is  to  estimate  the 
reading  correction  from  the  finding  for  distance  on  the  basis  of 
the  age  of  the  patient,  and  then  modify  the  correction,  if  neces- 
sary, until  the  patient  is  satisfied.  It  is  usually  assumed  that  the 
prescription  of  glasses  for  reading  is  an  easy  matter,  but  in  alto- 
gether too  large  a  proportion  of  these  cases  the  result  in  the  end  is 
not  satisfactory.  To  correct  theoretically  a  case  of  presbyopia  is 
simple  enough,  but  to  do  so  to  the  satisfaction  of  the  wearer  of 
the  glasses  is  quite  another  matter.  Suppose  we  take  the  case  of 
an  emmctrope,  or  one  who  is  nearly  so.  The  patient  has  had  to 
hold  the  print  farther  and  farther  from  his  eyes,  until  at  last  his 


I 


TESTS    FROM    THE    TRIAL    CASE.  63 

arms  are  too  short  for  the  purpose.  Under  these  circumstances 
he  is  forced  to  come  at  last  to  the  optometrist  for  glasses.  The 
latter  makes  his  tests  and  finds  the  distant  correction,  asks  the 
patient's  age,  and  then  figures  the  near  correction  on  the  basis  of  a 
reading  and  working  distance  of  13  inches.  Apparently  the  lenses 
are  excellent,  the  patient  is  delighted  and  feels  that  now  his  trou- 
bles are  over,  but  in  a  few  days  he  returns.  He  reports  that  he 
can  see  all  right  so  far  as  clearness  of  vision  is  concerned.  But 
that  he  simply  cannot  wear  the  glasses  prescribed ;  that  they  are 
not  his  fit ;  that  some  one  has  made  a  mistake.  The  cause  of  the 
trouble  is  this:  He  has  been  fitted  for  13  inches.  As  a  result 
of  previous  presbyopic  experience  he  has  learned,  unconsciously, 
that  to  see  at  this  short  distance  he  must  make  a  tremendous 
ocular  effort ;  and  in  spite  of  his  new  glasses  he  still  tries  to  make 
it ;  the  result  being  eyestrain.  To  relieve  the  disagreeable  symp- 
toms he  pushes  the  print  farther  back,  as  he  used  to,  but  this 
makes  the  type  either  blurred  or  not  so  distinct,  and  so  he  brings  it 
back  to  13  inches  again,  regardless  of  the  eyestrain,  until  he  loses 
patience  and  comes  back  to  get  the  "right  fit."  These  symptoms 
also  are  accentuated  by  the  strain  put  upon  his  convergence,  a  con- 
vergence which  he  has  not  used  to  such  an  extent  for  years.  So 
common  is  this  experience  in  a  more  or  less  marked  degree,  that 
there  are  many  optometrists  who,  when  asked  which  are  the  most 
difficult  cases  to  fit,  will  answer  promptly  ''presbyopic  ones." 

In  prescribing  glasses  for  reading  and  working,  to  get  the 
greatest  satisfaction,  there  are  several  points  to  be  taken  into  con- 
sideration; the  near  point  with  the  distance  correction  in  place; 
the  amplitude  of  accommodation ;  the  point  at  which  the  patient 
should  read  to  be  in  the  most  comfortable  position  ;  the  point  at 
which  he  has  previously  been  reading ;  and  most  important  of  ah, 


64  THE   TRIAL   CASE   AND    HOW    TO    USE   IT. 

the  glasses  which  he  has  been  wearing,  if  any.  The  distance  at 
which  the  patient  ought  to  read  ordinarily  depends  upon  his  build, 
unless  amblyopia  be  present,  but  when  he  has  been  reading  with 
arms  too  far  outstretched,  it  will  be  necessary  at  first  to  select  a 
new  point  only  a  little  inside  of  this,  even  if  it  does  seem  too  far 
away.  Later  he  will  have  to  return  and  get  stronger  lenses  which 
will  bring  his  reading  point  to  the  right  place. 

Where  the  presbyopic  patient  has  been  wearing  reading 
glasses  which  have  become  unsatisfactory,  it  will  usually  be  be- 
cause of  increasing  age  and  consequent  loss  of  accommodation, 
though  it  may  be  due  to  incipient  cataract  or  retinal  failure.  In 
these  cases  it  is  an  open  question  whether  it  is  always  necessary  to 
go  through  the  complete  routine  of  examination.  If  the  patient 
has  normal  vision  and  no  eyestrain  or  defects  of  vision  for  the 
working  distance,  except  that  his  glasses  are  no  longer  strong 
enough,  it  may  not  be  necessary  to  do  anything  more  than  to  add 
on  the  +  .50  or  +  I.  diopter  required,  but  where  the  vision  is  not 
normal  then  a  rigid  examination  is  usually  best,  though  if  the  test 
with  the  concave  retinoscopic  mirror  reveals  opacities  the  difficulty 
is  probably  cataract,  in  which  event  the  best  and  simplest  way 
is  to  decline  the  case  and  strongly  advise  the  eye  surgeon. 

THE  BINOCULAR  TEST  FOR  NEAR.— With  the  near 
correction  in  place  have  the  patient  take  in  his  hand  the  near  read- 
ing chart  and  hold  it  at  the  reading  distance  for  his  case.  Now 
cover  first  one  eye  and  then  the  other,  to  see  if  one  eye  sees  better 
than  the  other.  In  case  one  eye  is  better,  alter  the  correction  by 
an  additional  plus  or  minus  .25  or  more  to  try  to  make  both  eyes 
alike.  Try  tlit^  same  method  on  the  other  eye,  if  necessary.  If 
there  should  prove  to  be  considerable  difiference  in  refraction  of 


TESTS    FROM    THE    TRIAL    CASE.  65 

the  two  eyes  try  the  following:  Have  the  patient  watch  the 
smallest  letters  of  the  reading  chart ;  then  by  minus  lenses  of  low 
power  before  one  eye,  or  plus  lenses  of  low  power  before  the  other 
(in  addition  to  the  correction  already  in  place)  see  whether  there 
is  any  difference  in  the  comfortable  feeling  of  the  eyes  by  slight 
changes  in  the  power  of  either  eye.  It  will  usually  be  found  that 
where  the  difference  between  the  eyes  is  more  than  .25  D.,  that 
this  will  have  to  be  at  least  halved.  The  reason  why  there  should 
be  a  difference  in  the  eyes  at  short  distance  and  not  at  distance 
is  that  the  accommodation  of  the  two  eyes  does  not  always  work 
in  harmony.  Where  there  is  a  difference  between  the  two  eyes 
at  the  working  distance,  and  it  can  not  be  corrected  by  lenses,  then 
it  is  due  to  an  impairment  of  vision  and  the  patient  should  be 
so  told,  though  the  difference  will  often  be  so  slight  that  no  fur- 
ther attention  needs  to  be  given  to  the  matter. 

THE  TEST  FOR  SPECIAL  DISTANCE.— Patients  must 
sometimes  be  fitted  for  special  distances,  as,  for  instance,  musicians 
and  printers ;  for  the  former  the  test  chart  should  be  musical  notes 
of  various  sizes.  If  these  cases  are  simply  presbyopic  then  the 
matter  is  easily  arranged,  but  where  there  is  recent  amblyopia  due 
to  physiological  changes,  then  trouble  may  be  expected,  for 
it  will  be  found  that  when  the  very  best  correction  is  in  place, 
whether  for  type  or  musical  notes,  as  the  case  may  be,  the  patient 
will  not  see  sufficiently  well  for  his  purpose.  To  get  a  patient  of 
this  class  to  work  at  closer  range  than  the  specified  distance  is 
usually  impossible,  and  yet  stronger  lenses  cannot  be  prescribed 
unless  the  work  is  to  be  held  closer.  The  optical  rule  is  very 
simple ;  the  more  powerful  the  lens,  the  closer  the  print  must  be,  as 
is  quite  clear  when  we  consider  magnifying  glasses.     The  patient, 


66  THE   TRIAL  CASE   AND    HOW    TO    USE    IT. 

however,  as  described  here,  will  not  accept  any  such  dictum,  but 
demands  glasses  that  will  give  him  what  he  wants.  He  will 
claim  that  this  is  what  optometrists  are  for.  Of  the  same  general 
nature  as  the  above  is  the  patient  who  insists  on  reading  at  a 
certain  distance  when  the  condition  of  his  eyes,  usually  amblyopic, 
requires  that  he  read  at  a  shorter  point.  When  the  optometrist 
gets  a  patient  of  this  kind,  and  cannot  convince  him  of  the  natural 
limitations  of  lenses,  he  should  decline  to  have  anything  further 
to  do  with  the   case. 

FITTING  FOR  CLOSER  THAN  THIRTEEN  INCHES. 
— It  sometimes  happens  in  cases  of  amblyopia,  often  due  to 
cataract  or  abnormally  small  pupils,  that  the  patient  must  be  fitted 
for  a  much  closer  distance  than  13  inches.  Sometimes  it  has  to 
be  as  low  as  4  inches  or  less.  It  is  doubtful  as  to  whether  the 
optometrist  should  touch  these  rare  cases,  but  if  he  does  it  is 
better  to  fit  one  eye  only,  so  as  to  avoid  extraordinary  strain  of 
undue  convergence.  The  writer  has  fitted  a  case  of  this  kind, 
high  myopia  combined  with  extensive  cataract,  for  a  distance 
of  2  inches. 


CHAPTER  VII. 

VARIOUS   LENSES   USED  IN   GLASSES. 

A^ARIETIES  OF  LENSES.— The  standard  lenses  for  firsi- 
class  work  are  periscopic,  the  concavity  in  plus  lenses  being  on 
a  minus  curve  of  1.25  D.  of  power,  the  concavity  to  be  placed  next 
the  eye.     Where  there  is  a  minus  cylinder  present  and  the  axis  is 


VARIOUS   LENSES   USED   IN   GLASSES.  67 

horizontal,  the  cylindrical  side  of  the  lens  is  placed  towards  the 
eye.  In  glasses  for  myopia,  however,  which  have  a  plus  curve 
of  1.25  D.,  it  is  the  concave  side  which  is  placed  next  the  eye. 
In  other  cases  the  lenses  are  so  set  that  the  side  which  interferes 
the  least  with  the  up  and  down  motion  of  the  eyebrows  is  on 
the  inside.  Occasionally  periscopic  lenses  are  unsatisfactory,  and 
it  is  then  necessary  to  give  some  other  form,  such  as  plano- 
concave, bi-concave,  plano-convex  or  bi-convex,  as  the  case  may 
be.  Why  these  should  be  accepted  as  comfortable,  and  the  others 
not,  is  not  at  all  clear.  It  is  usually  stated  that  there  is  a  "glare" 
with  the  periscopic  form  which  does  not  exist  with  the  others, 
though  why  so  few  of  the  vast  number  of  those  who  wear  the 
periscopic  form  should  notice  this  "glare"  is  a  puzzle.  Some 
specialists  go  so  far  as  to  never  prescribe  periscopics. 

LENTICULAR  LENSES.— In  cases  of  high  ametropia, 
where  the  weight  of  the  lenses  prescribed  becomes  an  important 
factor  because  of  their  pressure  on  the  nose,  "lenticular"  lenses 
are  prescribed.     These  have  a  small  center  of  the  required  diop- 


Fig.    23. — Lenticular    Lenses. 

trie  power,  while  the  balance  of  the  lens  is  ground  down  to  a  thin 
glass  plate,  thus  reducing  the  weight  considerably.  It  is  true  that 
they  restrict  the  field  of  view,  but  this  does  not  seem  to  be  noticed 
by  those  who  wear  them. 

BIFOCALS.— Where  the  patient  must  wear  corrections  for 
both  far  and  near  vision,  two  pairs  can  be  described,  or  else 
bifocals.     There  are  several  forms  of  these,  as  may  be  seen  in 


68  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

any  dealer's  catalogue,  but  the  form  most  in  use  is  the  ''cement," 
these  having  proved  practically  to  be  the  most  satisfactory.  It 
takes  a  patient  some  little  time  to  get  used  to  bifocals,  as  the 
portion  corrected  for  reading  is  apt  to  get  in  the  way  when  the 
[)atient  looks  down.  This  is  especially  troublesome  when  he  is 
going  downstairs ;  in  fact,  the  patient  should  be  cautioned  in 
regard  to  this.  Once,  however,  accustomed  to  bifocals,  those 
who  wear  them  are  usually  pleased  and  unwilling  to  take  any 
others. 

CLERICAL  LENSES.— These  are  the  ordinary  style  of 
lenses,  periscopic  or  otherwise,  as  the  case  may  be,  with  the 
tops  ground  off.  They  take  the  place  of  a  bifocal  where  the 
patient  is  emmetropic,  or  nearly  so,  so  that  glasses  for  dis- 
tance are  not  needed.  Sometimes,  in  the  case  of  myopes,  they 
are  ground  the  other  way,  the  bottoms  off.  Occasionally  it  is 
also  necessary  to  cut  off  the  top  of  lenses  to  allow  them  to  set 
under  projecting  eyebrows.  These  lenses  take  their  name  from 
the  fact  that  they  are  used  principally  by  clergymen  in  the  pulpit. 

COQUILLES,  TORICS  AND  INVISIBLE  BIFOCALS.— 
These  are  three  forms  of  lenses  of  considerable  expense,  which 
for  those  who  can  afford  them  are  rapidly  coming  into  use.  The 
coquille  lens  is  a  shell-shaped  glass.  For  a  plus  i.  D.  it  might 
have  a  minus  curve  of  6  diopters  on  one  side  and  a  plus  7  on 
the  other.  The  outer  surface  of  these  lenses,  acting  as  a  rather 
strong  convex  mirror,  produces  an  effect  of  brilliancy  which  gives 
a  peculiar  charm  and  distinctiveness  to  the  face  of  the  wearer. 

THE  TORIC  LENS.— This  is  similar  to  the  coquille,  but 
corresponds  optically  to  a  sphero-cylinder.     On  one  surface  there 


VARIOUS   LENSES   USED    IN    GLASSES. 


69 


is  a  high  spherical  curve,  while  on  the  other  the  curvature  is 
that  of  a  tore.  Such  a  surface  v^hen  tested  v^ith  a  lens  measure 
will  show   different  power  in   different   meridians   on   the   same 


Fig.   24. — Toric   Curves. 


surface.  With  both  the  coquilles  and  the  toric  lenses  there  are 
sometimes  complaints,  similar  to  those  in  regard  to  periscopic 
lenses  ;  hence  it  is  necessary  sometimes  to  give  sphero-cylinders 
instead.  ■ 

THE  INVISIBLE  BIFOCALS  are  recent.  They  are  made 
of  three  pieces  of  glass,  two  crown  glass,  and  the  third  flint 
glass,  so  made  that  the  wafer  which  adds  the  power  for  near 
vision  is  entirely  inside  the  combination.  These  lenses  take  the 
place  of  the  usual  bifocal.  They  will  stand  rougher  usage  and 
make  a  better  appearance. 

TINTED  LENSES  AND  PLANOS.— Photophobia  or  in- 
tolerance of  light  is  usually  a  symptom  of  some  pathological  condi- 
tion, and  hence  the  cases  are  hardly  optometrical.  Nevertheless 
there  are  cases  where  the  patients  demand  these  glasses,  and  will 
have  them.  Under  these  circumstances  ''tinted"  glasses  will  be 
prescribed.  There  have  been  many  colors  and  tints  tried  for  this 
special  purpose   in  the  past,  but  in   view   of  the  nature   of  the 


70  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

retina  in  reference  to  the  waves  of  light,  smoke  is  the  only  tint 
that  should  be  used.  The  retina  is  adapted  for  the  reception 
of  all  the  component  parts  of  white  light,  and  smoke  glasses  do 
not  cut  any  of  these  off,  but  simply  reduce  the  intensity.  On  the 
contrary,  tinted  glass  deprives  the  retina  of  the  stimulus  of  the 
color  which  it  cuts  ofif,  or  absorbs,  and  this  produces  retinal 
fatigue,  and  if  the  wearing  of  the  colored  glass  is  persisted  in 
there  will  be  permanent  retinal  fatigue.  To  understand  what  is 
meant  by  retinal  fatigue  for  colors,  take  a  piece  of  blue  paper 
and  place  it  in  the  center  of  a  sheet  of  white  paper  in  a  bright 
light.  Stare  at  the  blue  paper  steadily  for  about  half  a  minute, 
then,  with  the  eyes  fixed,  withdraw  the  blue  paper.  In  a  moment 
or  so  a  strong  after  image  will  appear  on  the  white  paper  where 
the  blue  piece  had  been  placed.  This  will  be  of  reddish  color 
and  very  vivid.  It  means  that  the  white  light  from  the  card 
which  falls  on  that  spot  of  the  retina,  in  this  case  the  macula  lutea, 
where  the  image  of  the  blue  had  previously  been,  is  not  all  seen. 
We  do  not  see  the  blue  in  it,  for  the  eye  is  tired  for  blue.  What 
we  see  is  the  white  with  the  blue  left  out,  which  is  reddish.  This  is 
the  effect  that  wearing  colored  glasses  will  have.  Those  of  us 
who  have  gone  to  the  theatre  and  seen  the  play  of  the  calcium 
lights  will  recall  that  while  the  beauty  of  it  was  striking,  still  the 
return  of  the  while  light  was  always  a  relief. 

PRISMS. — These  are  prescribed  sometimes  in  heterophoria. 
A  large  percentage  of  cases  of  heterophoria  disappears  after  the 
correction  of  the  ametropia.  Some  authorities  claim  that  all 
heterophorias  are  due  to  refractive  errors,  and  that  prisms  should 
never  be  used ;  others  do  not  go  so  far  as  this,  but  in  any  event 
the  first  thing  to  do  in  heterophoria  is  to  correct  the  ametropia, 


VARIOUS   LENSES    USED   IN    GLASSES.  71 

and  then  wait  a  few  weeks.  In  other  cases  the  heterophoria  is  not 
noticed ;  it  gives  no  trouble,  and  therefore  no  attempt  should  be 
made  to  correct  it.  Aside  from  the  above-mentioned  cases,  there 
are  some  where  the  heterophoria  persists,  and  with  these  prisms 
should  under  certain  circumstances  be  prescribed.  These  cases 
will  not  be  discussed  here. 

KEEPING  RECORDS.— If  the  method  of  partial  correc- 
tion at  first,  and  the  gradual  increase  to  full  correction  later,  is 
followed,  as  recommended  here,  then  records  must  be  kept,  not 
only  of  the  lenses  which  are  prescribed,  but  of  the  dioptric  con- 
ditions on  which  such  prescriptions  are  founded.  As  to  the  style 
of  record  to  be  kept  each  one  should  devise  his  own.  In  it  there 
should  be  all  the  points  that  have  been  described  here,  including 
a  brief  history  of  the  case.  Such  a  record,  properly  indexed,  may 
save  a  great  deal  of  future  trouble,  as  well  as  the  necessity  of 
re-examinations. 


CHAPTER  VIII. 
SOME  USEFUL  INFORMATION. 

CHILDREN  AND  SCHOOL  LIFE.— It  is  an  open  question 
as  to  whether  the  eyes  of  many  children  are  equal  to  the  demands 
of  modern  civilization.  When  we  consider  the  age  of  the  world, 
and  then  the  development  of  modern  printing  and  its  use  in 
schools,  we  feel  that  it  is  going  to  take  many  thousands  of  years 
before  all  eyes  will  be  fully  altered  to  fit  the  continuance  of  pres- 
ent school  conditions.  Fine  print  and  sewing  are  bad  enough, 
especially  when  they  are  made  part  of  a  kindergarten  course,  but 


72  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

when  we  add  to  this  musical  notes  written  in  small  type  it  is 
not  at  all  strange  that  eyestrain  should  be  so  prevalent. 

In  the  case  of  books  used  in  schools,  there  has  been  a  steady 
improvement,  which  has,  however,  for  economical  reasons,  not 
yet  gone  far  enough.  Every  school  book  should  be  in  large  type, 
well  spaced,  with  narrow  columns,  and  not  on  glazed  paper.  This 
will  reduce  the  strain  on  the  vision  to  the  lowest  point.  But 
the  reform  should  not  stop  there.  There  is  the  question  of  desks. 
Every  child  should  have  a  desk  to  fit  him,  and  these  are  to  be 
had  in  the  market.  Some  schools  use  them.  Where  the  desks  do 
not  fit,  then  the  body,  not  being  properly  supported,  the  muscles 
begin  to  droop ;  the  child  to  be  comfortable  comes  too  near  to  his 
work,  and  eye  troubles  are  the  result.  In  other  cases,  however, 
the  weariness  of  the  effort  is  the  n;ain  point,  and  the  child  ceases 
to  be  a  scholar. 

Child  nature  has  been  studied  a  great  deal,  but  the  limi- 
tations of  children's  endurance  is  as  yet  not  one  of  the  courses 
given  to  teachers.  A  child  should  have  frequent  periods  of  rest ; 
a  great  deal  of  their  work,  especially  in  arithmetic,  should  be  done 
standing  at  blackboards  on  which  dustless  crayon  is  used ;  when 
small  they  should  have  no  home  tasks  at  all ;  in  the  grammar 
schools  these  tasks  should  be  light  and  few,  though  beyond  that 
point  they  seem  to  be  an  unavoidable  part  of  modern  school  life ; 
the  light  in  the  schools  should  be  of  the  right  kind  and  from  the 
correct  direction — from  the  left ;  under  no  circumstances  should 
their  eyes  face  the  light.  The  teacher  should  keep  records  of  the 
eyesight  of  the  pupils ;  not  scientific  records,  but  simple  ones  which 
will  not  require  on  her  part  more  than  an  hour  of  study  to  under- 
stand and  possibly  two  or  three  hours  of  the  whole  session  to 
make  and  keep.     In  the  case  of  those  children  who  fail  on  the 


SOME  USEFUL  INFORMATION.  73 

au.  pie  sight  tests  given,  notices  should  be  sent  to  the  parents, 
and  where  these  notices  are  not  noticed  they  should  be  fol- 
lowed up. 

MYOPIA — This  is  the  scientific  name  for  near-sightedness. 
A  near-sighted  child  can  see  well  near  by,  but  not  at  a  distance. 
Such  a  child  does  not  like  to  play  with  his  fellows,  as  he  is  always 
the  one  "caught."  Myopia  in  school  children  tends  to  grow  stead- 
ily worse.  The  myopia  may  develop  into  cases  of  disease,  and 
where  this  is  not  the  case  the  child  is  robbed  of  most  of  the  enjoy- 
ment of  life.  IMyopic  children  are  usually  unchildishly  sober  in 
demeanor. 

WHEN  SHOULD  A  CHILD  WEAR  GLASSES  ?— In  the 
first  place,  any  child  old  enough  to  study,  and  who  does  have  to 
study,  should  wear  glasses  if  his  eyes  are  not  normal.  This  will 
be  shown  in  several  ways:  DifBculty  in  seeing  either  near  or 
far ;  pains  in  the  eyes ;  headaches.  School  life  is  an  important 
piece  of  business,  and  since  almost  the  only  sense  used  in  schools 
is  the  eye,  and  this  sense  is  used  to  excess,  every  child's  eyes 
without  exception  should,  before  commencing  school  life,  be  exam- 
ined in  order  to  see  to  what  extent  he  is  prepared  to  take  up 
the  work.  Knowledge  under  modern  conditions  is  an  absolute 
necessity,  but  so  is  vision,  hence  no  chances  should  be  taken.  The 
idea  that  all  eyes  are  right  and  more  or  less  alike  is  about  as  true 
as  to  say  that  all  people  should  be  of  the  same  height  or  weight,  or 
color  of  hair,  or  state  of  health. 

OVERWORKING  THE  EYES.— It  is  strange  how  some 
people  will  overwork  their  eyes.  They  will  rest  their  backs  when 
tired,  but  for  a  tired  eye  they  have  no  mercy.     They  will  not 


74  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

subject  their  voices  to  exercise,  by  screaming,  for  instance,  but 
they  will  read  on  the  cars,  or  read  when  sleepy,  or  do  fine  work, 
not  because  they  have  to,  but  because  they  take  pleasure  in  it, 
though  the  eyes  are  rebelling  all  the  time.  They  will  read  poor 
type,  and  small  type,  though  their  eyes  are  meantime  on  a  con- 
tinual strain.  None  of  these  things  ought  to  be  done,  as  they 
force  the  owner  of  the  eyes  to  wear  spectacles  sooner  than  would 
otherwise  be  the  case,  yet  every  one  with  normal  eyes  must  wear 
glasses  for  reading  sooner  or  later.  That  is  the  order  of  nature. 
But  though  no  one  likes  the  idea  of  putting  on  glasses,  still  he 
will  do  those  very  things  which  make  the  wearing  of  glasses 
unduly  early  a  necessity.  When  such  a  one  is  forced  to  come  at 
last  to  the  optometrist,  and  wonders  why,  the  reason  is  simple. 
He  has  overworked  his  eyes  and  must  pay  the  penalty. 

WHEN  SHOULD  GLASSES  BE  WORN?— When  one 
does  not  recognize  his  friends  on  the  street ;  when  he  has  to  turn 
the  light  very  high  to  see  to  read ;  when  he  has  to  hold  the  print 
too  far  away  from  his  eyes ;  when  he  has  to  hold  the  print  under 
his  nose ;  when  his  eyes  ache  or  water !  when  he  has  headaches 
which  headache  powders  won't  cure;  when  things  look  misty  or 
double;  when  his  eyes  trouble  him  in  this  way  it  is  time  for 
him  to  have  them  examined. 

DROPS  IN  THE  EYES.— This  is  the  expression  used 
when  atropine  or  similar  substance  is  put  in  the  eye.  Atropine 
is  a  powerful  poison.  It  is  the  alkaloid  from  belladonna  just 
as  morphine  is  the  alkaloid  from  opium.  We  should  no  more 
think  of  having  this  powerful  drug  put  in  our  eye  than  we  would 
to  take  chloroform  or  ether.     Both  ether  and  atropine  have  their 


SOME  USEFUL  INFORMATION.  75 

places,  but  intelligent  people  should  be  slow  to  consent  to  their 
use.  It  is  true  that  those  who  make  use  of  atropine  belittle  its 
effects;  nevertheless  it  is  dangerous,  and  sometimes  produces 
untoward  results. 

PARAFFIN  INJECTIONS  TO  IMPROVE  THE  SHAPE 
OF  THE  NOSE. — The  ey€  is  an  organ* with  a  circulatory  system. 
If  the  circulation  stops,  the  eye  will  grow  blind.  There  is  danger 
in  the  modern  practice  of  injecting  paraffin  under  the  skin  for 
cosmetic  purposes.  Some  of  the  veins  from  the  eye  pass  down 
through  the  base  of  the  nose.  In  a  recent  case  one  of  these  veins 
was  plugged  by  a  piece  of  paraffin  in  injections  as  above  stated, 
and  the  result  was  total  blindness  in  a  few  hours. 

SECOND  SIGHT. — Some  elderly  people  regain  their  vision 
by  what  is  called  second  sight.  This  is  an  abnormal  condition  of 
the  lens  of  the  eye,  in  which  it  swells  and  gains  magnifying  power. 
In  some  cases  second  sight  is  permanent  and  a  great  comfort,  but 
usually  it  is  followed  by  slowly  failing  vision,  until,  if  the  person 
lives  long  enough,  there  is  blindness. 

WHAT  TO  DO  WITH  AN   INFLAMED  EYE. 

NATURE  OF  INFLAMMATION.— There  are  three  kinds 
of  eye  inflammations :  Severe  accident,  disease,  and  mechanical 
irritation  due  to  the  presence  of  some  foreign  particle.  In  the 
first  two  cases  the  party  should  get  to  a  doctor  without  the  slight- 
est delay.  In  the  third  case  he  should  be  recommended  to  go  to 
a  doctor,  but  if  he  will  not,  ordinary  human  feeling  demands  that 
we  do  something.     Suppose  there  is  lime  in  the  eye,  wash  the  eye 


76 


THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 


with  a  solution  of  vinegar  in  water,  a  teaspoonful  to  a  cup  of 
water,  or  olive  oil  may  be  used,  whichever  can  be  had  the  first. 
In  case  of  burns  by  acids,  use  lime  water  from  the  druggist  or 
milk  is  just  as  good.  In  severe  cases  the  doctor  should  have 
been  sent  for  whether  the  patient  agrees  or  not,  for  the  injuries 
are  apt  to  be  very  serious ;  and  this  applies  with  especial  force 
to  pieces  of  metal  which  have  sunk  into  the  surface  of  the  eye. 

DUST  OR  SAXD  OR  CINDER  IX  THE  EYE.— This  is  a 
very  common  occurrence,  and  every  one  should  know  what  to  do 
to  help  the  sufferer.  As  a  matter  of  fact,  dust  is  getting  into  the 
eyes  all  the  time,  but  tears  and  winking  keep  working  it  out. 


Fig.  25. — Removing  the  Cinder. 


Unconsciously  we  rub  our  eyes  a  great  many  times  every  day 
to  get  rid  of  this  dust,  which  gathers,  moistened  by  the  natural 
tears  of  the  eye,  at  the  inner  canthus.  When,  however,  something 
<iharp  gets  into  the  eye,  a  cinder,  for  instance,  it  is  apt  to  catch 


SOME  USEFUL  INFORMATION.  77 

cither  on  the  under  surface  of  the  cycHd,  usually  the  upper  one, 
or  the  cornea  itself.  The  old  woman's  way  to  get  rid  of  it  is 
to  pull  out  the  upper  lid,  and  suddenly  insert  her  tongue  into 
the  cavity.  Not  a  very  pleasant  method,  but  often  very  effective. 
Another  way  is  to  run  the  loop  of  a  horsehair  in  and  draw  it 
across  the  ball  of  the  eye.  This  is  dangerous,  as  the  eye  is  apt 
to  be  infected.  Some  druggists  sell,  or  used  to  sell,  what  is  called 
"eye-stones,"  little  flat,  smooth  stones  about  the  size  of  the  scale 
of  a  fish,  which  would  be  inserted  under  the  upper  lid,  and  which 
by  their  movements  from  place  to  place,  because  of  the  continual 
turning  of  the  eyeball,  would  carry  out  the  obstruction.  Some- 
times when  the  druggist  would  be  out  of  eyestones  he  would  fur- 


FiG.    26. — A   Special  Tool  for  Everting  the  Eyelid. 

nish  a  small  seed  for  the  purpose.  Here  again  there  is  danger 
of  infection.  Still  another  way  is  to  pull  out  the  lid  and  blow 
into  the  eye.  The  best  way  to  proceed,  however,  is  as  follows: 
Bring  the  patient  near  a  bright  light ;  but  if  the  examiner's  eyes 
are  presbyopic,  and  he  cannot  see  well  at  a  close  range,  say 
6  inches,  he  should  put  on  a  pair  of  spectacles  which  will  permit 
him  to  do  so,  or  else  use  a  jeweler's  loupe ;  pull  out  the  lower  lid 
and  see  if  the  irritating  particle  is  there ;  sometimes  it  is  not,  as  the 
patient  himself  will  have  removed  it  by  the  rubbing.  Now  evert 
the  upper  eyelid,  stick  a  hairpin  in  a  cork,  catch  with  the  fingers  of 
one  hand  the  edge  of  the  upper  lid ;  touch  the  center  of  the  lid 
with  the  curve  of  the  hairpin  of  the  cork,  and  turn  the  eyelid 


78  THE    TRIAL    CASE    AND    HOW    TO    USE    IT. 

inside  out.  The  cinder  or  other  matter,  if  not  already  out,  will 
be  seen  at  once,  and  can  be  removed  with  the  tip  of  a  clean  hand- 
kerchief or  a  tuft  of  absorbent  cotton.  Remember  that  the  irri- 
tation will  cause  the  eye  to  be  painful  for  some  time,  even  when 
the  cinder  has  been  removed ;  also  that  with  all  your  care  and 
searching  the  particle  may  be  so  small  that  you  cannot  find  it ;  or  it 
may  be  so  imbedded  that  you  cannot  remove  it;  in  either  case  try 
to  get  the  patient  to  go  to  the  doctor  for  a  healing  collyrium.  He 
may  not  take  your  advice,  but  at  least  you  have  done  your  duty. 

HANDLING  LENSES.— Lenses  should  never  be  touched 
by  the  fingers,  as  this  soils  them,  which  in  turn  may  lead  to  errors 
in  the  subjective  tests.  They  should  be  kept  clean  by  the  use  of 
a  fresh  cloth  each  day,  and  should  be  removed  from  the  trial  case 
and  returned  thereto  by  the  handles  only. 


t- 


APPENDIX 


MEASUREMENTS  OP  THE  EYE    {Jaeger). 

Anterior-posterior    diameter    24.3  mm. 

Horizontal  diameter   23.6  mm. 

Vertical    diameter    23.4  mm. 

Diameter   of   cornea 12      mm. 

Average  thickness    of  cornea 1      mm. 

Average   diameter  of  pupil 4     mm. 

Average  diameter  of  optic  nerve  through  sclerotic 1.5  mm. 

Thickness   of  crystalline   lens 3.7  mm. 

Diameter  of  crystalline   lens 10.3  mm. 

XoTE. — A  millimeter   (mm.)   is  very  close  to  1-25  inch. 

APPROXIMATE   PERCENTAGES   OF  VISUAL   CONDITIONS   IN 

DARK  ROOM. 

Per  cent. 

Emmetropia    4 

Hyperopia     30 

Myopia     4 

Simple  hyperopic  astigmatism   10 

Simple    myopic   astigmatism 2 

Compound   hyperopic    astigmatism 45 

Compound    myopic    astigmatism 3 

Mixed    astigmatism ., 2 

100 

TEST  TYPES  FROM  PRINTERS'  FONTS  {Jaeger). 

No.  1 — Diamond.  No.  8 — Pica. 

No.  2— Pearl.  No.  9 — Two-line  Brevier. 

No.  3— Nonpareil.  No.  10 — Two-line  Long  Primer. 

No.  4— Minion.  No.  11 — Two-line  Pica. 

No.  5 — Brevier.  No.  12 — Three-line  Pica. 

No.  6— Long  Primer.  No.  13 — Four-line  Pica. 

No.  7— Small  Pica.  No.  14— Five-line  Pica. 

TEST  TYPES    (Snellen.) 

200  ft.  3^  in.  square.  40  ft.  ^  in.  square. 

160  ft.  3       in.  square.  30  ft.  9-16  in.  square. 

120  ft.  2%  in.  square.  20  ft.  ^  in.  square. 

100  ft.  1^  in.  square.  15  ft.  9-32  in.  square. 

80  ft.  VA  in.  square.  10  ft.  3-16  in.  square. 

60  ft.  lii  in.  square.  7^  ft.  9-64  in.  square. 


RECORD  OF  CASES. 

Xame     

Address    

Date 

HISTORY. 

Difficulty  in  seeing  far  ? 

Difficulty  in  seeing  near  ? 

Headaches  ?   

Eye-tire  ?    

Winking  ?    

Flow  of  tears  ? 

Photophobia  ?    

Sore  eyes  in  morning  ? 

Diplopia  ?    

Special    symptoms  ? 

R.  E.  Finding : 

L.  E.  Finding : 

R.  E.  Prescription  for  distance • 

L.  E.  Prescription  for  distance 

R.  E.  Prescription  for  near inches 

L.  E.  Prescription  for  near inches 

Note. — The  above  is  a  record  of  the  case  kept  by  the  optom- 
etrist for  future  reference.  It  is  distinct  from  the  prescription 
order  sent  to  the  shop  to  be  filled. 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 
0?Ta"^£TRY  LIBRARY 


This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 

Renewed  books  are  subject  to  immediate  recall. 


1 

T  n  91    /«n»v,  o  'RQ                                General  Library 

V 


U.C.  BERKELEY  LIBRARIES 


CDE5T4m3E 


